Storage can be specified on a per-spec basis.

If not defined on the spec, IKOptions.default_storage will be used. If that's
not defined, it will fall back to the image field's storage.

imagekit/options.py

@@ -20,6 +20,12 @@ class Options(object):
 
     """
 
+    default_storage = None
+    """Storage used for specs that don't define their own storage explicitly.
+    If neither is specified, the image field's storage will be used.
+
+    """
+
     crop_horz_field = 'crop_horz'
     crop_vert_field = 'crop_vert'
     preprocessor_spec = None
@@ -28,7 +34,6 @@ class Options(object):
     cache_filename_fields = ['pk', ]
     cache_filename_format = "%(filename)s_%(specname)s.%(extension)s"
     specs = None
-    #storage = defaults to image_field.storage
 
     def __init__(self, opts):
         for key, value in opts.__dict__.iteritems():

imagekit/specs.py

@@ -20,6 +20,7 @@ class ImageSpec(object):
     pre_cache = False
     quality = 70
     increment_count = False
+    storage = None
 
     def __init__(self, processors=None, **kwargs):
         if processors:
@@ -116,7 +117,9 @@ class Accessor(object):
 
     @property
     def _storage(self):
-        return getattr(self._obj._ik, 'storage', self._imgfield.storage)
+        return getattr(self.spec, 'storage', None) or \
+            getattr(self._obj._ik, 'default_storage', None) or \
+            self._imgfield.storage
 
     @property
     def url(self):