diff --git a/imagekit/management/commands/warmimagecache.py b/imagekit/management/commands/warmimagecache.py
index 42a005d..dfe5d46 100644
--- a/imagekit/management/commands/warmimagecache.py
+++ b/imagekit/management/commands/warmimagecache.py
@@ -19,17 +19,16 @@ class Command(BaseCommand):
 
         for generator_id in generators:
             self.stdout.write('Validating generator: %s\n' % generator_id)
-            for cacheables in cacheable_registry.get(generator_id):
-                for cacheable in cacheables.files():
-                    if cacheable:
-                        generator = generator_registry.get(generator_id, cacheable=cacheable)  # TODO: HINTS! (Probably based on cacheable, so this will need to be moved into loop below.)
-                        self.stdout.write('  %s\n' % cacheable)
-                        try:
-                            # TODO: Allow other validation actions through command option
-                            GeneratedImageCacheFile(generator).validate()
-                        except Exception, err:
-                            # TODO: How should we handle failures? Don't want to error, but should call it out more than this.
-                            self.stdout.write('    FAILED: %s\n' % err)
+            for kwargs in cacheable_registry.get(generator_id):
+                if kwargs:
+                    generator = generator_registry.get(generator_id, **kwargs)  # TODO: HINTS! (Probably based on cacheable, so this will need to be moved into loop below.)
+                    self.stdout.write('  %s\n' % generator)
+                    try:
+                        # TODO: Allow other validation actions through command option
+                        GeneratedImageCacheFile(generator).validate()
+                    except Exception, err:
+                        # TODO: How should we handle failures? Don't want to error, but should call it out more than this.
+                        self.stdout.write('    FAILED: %s\n' % err)
 
     def compile_patterns(self, generator_ids):
         return [re.compile('%s$' % '.*'.join(re.escape(part) for part in id.split('*'))) for id in generator_ids]
diff --git a/imagekit/registry.py b/imagekit/registry.py
index 93e491f..258f252 100644
--- a/imagekit/registry.py
+++ b/imagekit/registry.py
@@ -70,25 +70,25 @@ class CacheableRegistry(object):
         Associates cacheables with a generator id
 
         """
-        for cacheable in cacheables:
-            if cacheable not in self._cacheables:
-                self._cacheables[cacheable] = set()
-            self._cacheables[cacheable].add(generator_id)
+        if cacheables not in self._cacheables:
+            self._cacheables[cacheables] = set()
+        self._cacheables[cacheables].add(generator_id)
 
     def unregister(self, generator_id, cacheables):
         """
         Disassociates cacheables with a generator id
 
         """
-        for cacheable in cacheables:
-            try:
-                self._cacheables[cacheable].remove(generator_id)
-            except KeyError:
-                continue
+        try:
+            self._cacheables[cacheables].remove(generator_id)
+        except KeyError:
+            pass
 
     def get(self, generator_id):
-        return [cacheable for cacheable in self._cacheables
-                if generator_id in self._cacheables[cacheable]]
+        for k, v in self._cacheables.items():
+            if generator_id in v:
+                for cacheable in k():
+                    yield cacheable
 
     def before_access_receiver(self, sender, generator, cacheable, **kwargs):
         generator.image_cache_strategy.invoke_callback('before_access', cacheable)
@@ -130,8 +130,6 @@ class Register(object):
 
     # iterable that returns kwargs or callable that returns iterable of kwargs
     def cacheables(self, generator_id, cacheables):
-        if callable(cacheables):
-            cacheables = cacheables()
         cacheable_registry.register(generator_id, cacheables)
 
 
@@ -144,8 +142,6 @@ class Unregister(object):
         generator_registry.unregister(id, generator)
 
     def cacheables(self, generator_id, cacheables):
-        if callable(cacheables):
-            cacheables = cacheables()
         cacheable_registry.unregister(generator_id, cacheables)
 
 
diff --git a/imagekit/specs/sourcegroups.py b/imagekit/specs/sourcegroups.py
index 6bd1eed..04c30c3 100644
--- a/imagekit/specs/sourcegroups.py
+++ b/imagekit/specs/sourcegroups.py
@@ -117,11 +117,8 @@ class ImageFieldSourceGroup(object):
         self.image_field = image_field
         signal_router.add(self)
 
-    def files(self):
-        for instance in self.model_class.objects.all():
-            yield getattr(instance, self.image_field)
-
     def __call__(self):
-        return self.files()
+        for instance in self.model_class.objects.all():
+            yield {'source': getattr(instance, self.image_field)}
 
 signal_router = ModelSignalRouter()