this sounds like a safari specific issue. i know exactly what's causing it, but was under the impression safari would be smart enough to read the file mime type, and display the images based on that.
the work around until this gets fixed, is to use a "proper" browser such as chrome or firefox. I'll work on updating the code to fix this safari hiccup for the next ubbt release.
thanks for reporting this, and the other safari related item from earlier today
