!img! tag can result in wrong images used
tags to display attached images in a wiki page can pick up the wrong image because there seems to be some kind of matching involved.
Example: if there are two files "button.png" and "v_button.png" and one uses to display the first picture, the second one will be displayed.
See http://redmine.lighttpd.net/projects/lighttpd/wiki/PromotionalArtwork where the first group of pictures is the same as the second while the second having different filenames (prefix "v_").
A solution would be to not use matching in order to find the file in question.