diff --git a/boards/models/attachment/__init__.py b/boards/models/attachment/__init__.py
--- a/boards/models/attachment/__init__.py
+++ b/boards/models/attachment/__init__.py
@@ -6,18 +6,12 @@ from random import random
 
 from django.db import models
 
-from boards.models.attachment.viewers import AbstractViewer, WebmViewer, \
-    AudioViewer, SvgViewer
+from boards.models.attachment.viewers import get_viewers, AbstractViewer
+
 
 FILES_DIRECTORY = 'files/'
 FILE_EXTENSION_DELIMITER = '.'
 
-VIEWERS = (
-    WebmViewer,
-    AudioViewer,
-    SvgViewer,
-)
-
 
 class AttachmentManager(models.Manager):
     def create_with_hash(self, file):
@@ -65,7 +59,7 @@ class Attachment(models.Model):
 
     def get_view(self):
         file_viewer = None
-        for viewer in VIEWERS:
+        for viewer in get_viewers():
             if viewer.supports(self.mimetype):
                 file_viewer = viewer(self.file, self.mimetype)
                 break
diff --git a/boards/models/attachment/viewers.py b/boards/models/attachment/viewers.py
--- a/boards/models/attachment/viewers.py
+++ b/boards/models/attachment/viewers.py
@@ -11,6 +11,10 @@ FILE_TYPES_AUDIO = (
 )
 
 
+def get_viewers():
+    return AbstractViewer.__subclasses__()
+
+
 class AbstractViewer:
     def __init__(self, file, file_type):
         self.file = file