I think the missing http:// is what makes http://musicbrainz.org/release/9a5be08f-bb76-4a8c-824b-7e1d225e0fbe not show the coverart.
For some reason, it doesn't always prevent the cover art from loading, e.g. http://musicbrainz.org/release/5ef08648-db92-4c12-b0a2-abac6081778c/relationships.
Note that it's possible to get around the limitation by disabling JS (e.g., with noscript on firefox). Assuming that embedded http:// is valid in URLs, I think it should be allowed.
Well, the URL you want to use doesn't work either...
Thanks for testing this. Could it be because the image is too large?
Regardless, I do think we should be able to enter URLs with embedded http://.
I've experienced this too trying to paste-in archive.org links, which themselves contain http:// in the path (and don't support URL encoding of any of the characters). I worked around it by routing around the JS "correction" code.