Default image is a 404 on default configuration.

[kaladay]

Describe the bug
A 404 is being returned by the server for the default image.

To Reproduce
Steps to reproduce the behavior:

1. Go to a discovery view that renders images.
2. See broken image for thumbnails (before the actual thumbnail downloads and renders).

Expected behavior
While the discovery view page is loading the default image should appear rather than a broken image.

This is not a noticeable problem when the thumbnails load fast.