[Ulathar]

I might be misunderstanding your problem, but you should just be able to call up the Context Menu on the source icon and change artwork. If the artwork if saved in the correct location, it will become immediately available for selection. If it is saved elsewhere, then you have to go hunting for it.

Sorry I might have been a little unclear about that, but I appreciate your effort . I think I figured it out now. My problem wasn't directly related to the Xonfluence Skin like I thought but was indeed related to my Thumbsxx.db in which the OLD file paths to the thumbnails and thus the folder icons are stored.
Found a tool to read and modify those files and right now i try to substitude the file paths in there, too. I guess that will fix my missing icon problem but is quite a lot of work *sigh*.
 

I use an addon called Artwork Beef which I can use to either change the current artwork or to download other choices.  Now in my Context Menu for a show or a series I get the option to add more artwork or to select new artwork which carries me through.  The other way is via the Context Menu for a Show or a Series select "Manage" which allows you to select your preferred artwork.  But I guess you do this anyway.  If you know the title of one of your own art files, use the 'search' function in windows and see where those files are hidden.

Thanks, but my problem is not that I can't set new artworks but that I lost my previously set once because I had to move my files (paths changed) which was quite a lot of work. But like I said above, I guess I figured out how to fix it now.