diff --git a/wagtail/admin/templates/wagtailadmin/account/change_avatar.html b/wagtail/admin/templates/wagtailadmin/account/change_avatar.html
index 2044ea8da..4d9c492ac 100644
--- a/wagtail/admin/templates/wagtailadmin/account/change_avatar.html
+++ b/wagtail/admin/templates/wagtailadmin/account/change_avatar.html
@@ -9,7 +9,7 @@
     <div class="nice-padding">
         <p>{% trans "Your current profile picture:" %}</p>
         <p>
-            <span class="avatar square"><img src="{% avatar_url request.user size=50 %}"></span>
+            <span class="avatar square"><img src="{% avatar_url request.user size=50 %}" alt=""></span>
         </p>
 
         <form action="{% url 'wagtailadmin_account_change_avatar' %}" method="POST" enctype="multipart/form-data">
diff --git a/wagtail/admin/templates/wagtailadmin/pages/edit.html b/wagtail/admin/templates/wagtailadmin/pages/edit.html
index 2ada89bbb..a863a262f 100644
--- a/wagtail/admin/templates/wagtailadmin/pages/edit.html
+++ b/wagtail/admin/templates/wagtailadmin/pages/edit.html
@@ -69,7 +69,7 @@
                             {% blocktrans with last_mod=page.get_latest_revision.created_at %}Last modified: {{ last_mod }}{% endblocktrans %}
                             {% if page.get_latest_revision.user %}
                                 {% blocktrans with modified_by=page.get_latest_revision.user.get_full_name|default:page.get_latest_revision.user.get_username %}by {{ modified_by }}{% endblocktrans %}
-                                <span class="avatar small"><img src="{% avatar_url page.get_latest_revision.user size=25 %}" /></span>
+                                <span class="avatar small"><img src="{% avatar_url page.get_latest_revision.user size=25 %}" alt="" /></span>
                             {% endif %}
                             <a href="{% url 'wagtailadmin_pages:revisions_index' page.id %}" class="underlined">{% trans 'Revisions' %}</a>
                         {% endif %}
diff --git a/wagtail/admin/templates/wagtailadmin/pages/revisions/list.html b/wagtail/admin/templates/wagtailadmin/pages/revisions/list.html
index d22554b8f..9bab02ad1 100644
--- a/wagtail/admin/templates/wagtailadmin/pages/revisions/list.html
+++ b/wagtail/admin/templates/wagtailadmin/pages/revisions/list.html
@@ -22,7 +22,7 @@
                         <h2>
                             <a href="{% url 'wagtailadmin_pages:revisions_revert' page.id revision.id %}">{{ revision.created_at }}</a>
                             <span class="unbold">
-                                {% trans 'by' context 'points to a user who created a revision' %}<span class="avatar small"><img src="{% avatar_url revision.user size=25 %}" /></span>{{ revision.user }}
+                                {% trans 'by' context 'points to a user who created a revision' %}<span class="avatar small"><img src="{% avatar_url revision.user size=25 %}" alt="" /></span>{{ revision.user }}
                             </span>
                             {% if revision == page.get_latest_revision %}({% trans 'Current draft' %}){% endif %}
                             {% if revision == page.live_revision %}({% trans 'Live version' %}){% endif %}
diff --git a/wagtail/admin/templates/wagtailadmin/shared/main_nav.html b/wagtail/admin/templates/wagtailadmin/shared/main_nav.html
index f5def9f12..2780d7044 100644
--- a/wagtail/admin/templates/wagtailadmin/shared/main_nav.html
+++ b/wagtail/admin/templates/wagtailadmin/shared/main_nav.html
@@ -7,7 +7,7 @@
         <li class="footer" id="footer">
             <div class="account" id="account-settings" title="{% trans 'Edit your account' %}">
                 <span class="avatar square avatar-on-dark">
-                    <img src="{% avatar_url request.user size=50 %}" />
+                    <img src="{% avatar_url request.user size=50 %}" alt="" />
                 </span>
                 <em class="icon icon-arrow-up-after">{{ request.user.first_name|default:request.user.get_username }}</em>
             </div>
diff --git a/wagtail/admin/templates/wagtailadmin/shared/user_avatar.html b/wagtail/admin/templates/wagtailadmin/shared/user_avatar.html
index 8891e00f4..9d62e92e5 100644
--- a/wagtail/admin/templates/wagtailadmin/shared/user_avatar.html
+++ b/wagtail/admin/templates/wagtailadmin/shared/user_avatar.html
@@ -1,7 +1,7 @@
 {% load wagtailadmin_tags %}
 
 <span class="avatar small">
-    <img src="{% avatar_url user size=25 %}" />
+    <img src="{% avatar_url user size=25 %}" alt="" />
 </span>
 
 {{ user }}
diff --git a/wagtail/contrib/styleguide/templates/wagtailstyleguide/base.html b/wagtail/contrib/styleguide/templates/wagtailstyleguide/base.html
index dba447562..e99276d9b 100644
--- a/wagtail/contrib/styleguide/templates/wagtailstyleguide/base.html
+++ b/wagtail/contrib/styleguide/templates/wagtailstyleguide/base.html
@@ -780,9 +780,9 @@
             <h2>Misc formatters</h2>
             <h3>Avatar icons</h3>
 
-            <p><span class="avatar"><img src="{% avatar_url user size=50 %}" /></span> Avatar normal</p>
-            <p><span class="avatar square"><img src="{% avatar_url user size=50 %}" /></span> Avatar square</p>
-            <p><span class="avatar small"><img src="{% avatar_url user size=25 %}" /></span> Avatar small</p>
+            <p><span class="avatar"><img src="{% avatar_url user size=50 %}" alt="" /></span> Avatar normal</p>
+            <p><span class="avatar square"><img src="{% avatar_url user size=50 %}" alt="" /></span> Avatar square</p>
+            <p><span class="avatar small"><img src="{% avatar_url user size=25 %}" alt="" /></span> Avatar small</p>
 
             <h3>Status tags</h3>
             <div class="status-tag primary">Primary tag</div>
@@ -793,12 +793,12 @@
             <p>Add the following <code>div</code> around any items you wish to display with a spinner overlay and fading out</p>
             <p>Remove the "loading" class to disable the effect</p>
             <div class="loading-mask loading" style="width:200px">
-                <img src="{% static 'wagtailadmin/images/wagtail-logo.svg' %}" width="200" />
+                <img src="{% static 'wagtailadmin/images/wagtail-logo.svg' %}" width="200" alt="Wagtail" />
             </div>
 
             <h3>Image transparency</h3>
             <p>It can be useful to show users the transparent areas of images. Add a transparency checkerboard with the <code>.show-transparency</code> on the <code>img</code> tag thus:</p>
-            <img src="{% static 'wagtailadmin/images/wagtail-logo.svg' %}" width="200" class="show-transparency" />
+            <img src="{% static 'wagtailadmin/images/wagtail-logo.svg' %}" width="200" class="show-transparency" alt="Wagtail" />
         </section>
 
         <section id="icons" class="icons">
diff --git a/wagtail/images/templates/wagtailimages/widgets/compare.html b/wagtail/images/templates/wagtailimages/widgets/compare.html
index 3627a876a..14f4c901a 100644
--- a/wagtail/images/templates/wagtailimages/widgets/compare.html
+++ b/wagtail/images/templates/wagtailimages/widgets/compare.html
@@ -32,7 +32,7 @@
         {% if image_a %}
             {% image image_a max-165x165 class="show-transparency" %}
         {% else %}
-            <img>
+            <img alt="">
         {% endif %}
     </div>
 {% endif %}
diff --git a/wagtail/images/templates/wagtailimages/widgets/image_chooser.html b/wagtail/images/templates/wagtailimages/widgets/image_chooser.html
index 96f007baa..33f44f71c 100644
--- a/wagtail/images/templates/wagtailimages/widgets/image_chooser.html
+++ b/wagtail/images/templates/wagtailimages/widgets/image_chooser.html
@@ -8,7 +8,7 @@
         {% if image %}
             {% image image max-165x165 class="show-transparency" title=image.title %}
         {% else %}
-            <img>
+            <img alt="">
         {% endif %}
     </div>
 {% endblock %}
diff --git a/wagtail/users/templates/wagtailusers/users/list.html b/wagtail/users/templates/wagtailusers/users/list.html
index 8123ade12..4bdd62604 100644
--- a/wagtail/users/templates/wagtailusers/users/list.html
+++ b/wagtail/users/templates/wagtailusers/users/list.html
@@ -34,7 +34,7 @@
             <tr>
                 <td class="title" valign="top">
                     <h2>
-                        <span class="avatar small"><img src="{% avatar_url user size=25 %}" /></span>
+                        <span class="avatar small"><img src="{% avatar_url user size=25 %}" alt="" /></span>
                         <a href="{% url 'wagtailusers_users:edit' user.pk %}">{{ user.get_full_name|default:user.get_username }}</a>
                     </h2>
                     <ul class="actions">