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
@@ -48,7 +48,7 @@ class Attachment(models.Model):
         if file_viewer is None:
             file_viewer = AbstractViewer
 
-        return file_viewer(self.file, self.mimetype).get_view()
+        return file_viewer(self.file, self.mimetype, self.hash).get_view()
 
     def __str__(self):
         return self.file.url
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
@@ -39,9 +39,10 @@ def get_viewers():
 
 
 class AbstractViewer:
-    def __init__(self, file, file_type):
+    def __init__(self, file, file_type, hash):
         self.file = file
         self.file_type = file_type
+        self.hash = hash
 
     @staticmethod
     def supports(file_type):
@@ -115,6 +116,7 @@ class ImageViewer(AbstractViewer):
         return '<a class="{}" href="{full}">' \
                '<img class="post-image-preview"' \
                ' src="{}"' \
+               ' alt="{}"' \
                ' width="{}"' \
                ' height="{}"' \
                ' data-width="{}"' \
@@ -122,6 +124,7 @@ class ImageViewer(AbstractViewer):
                '</a>' \
             .format(CSS_CLASS_THUMB,
                     thumb_url,
+                    self.hash,
                     str(pre_width),
                     str(pre_height), str(width), str(height),
                     full=self.file.url, image_meta=metadata)