Nice work on the implementation of the skins wuischke, cool! (I just built a new CVS, was still working with a CVS of May this year which hasn't had it implemented yet). Because Fedora 7 uses blue versions of the Gnome folders in the default theme (other then that they use the default gnome theme), the aMule Fedora skin fits nicer with the Fedora 7 theme then the Gnome skin does. So I hope you can reconsider this and you would also include the Fedora skin.
I've updated the Tango skin which makes use of a different preferences icon which I agree with mischamajskij is a better icon to use. You can find the updated skin as attachment of this post.