Sorry, short post since I'm in a hurry and at work but I felt I should post ASAP. =)
1. It looks awesome. I personally had small cover thumbnails in mind originally, but given the purpose of the tool it doesn't seem all that necessary.
2. Oh right, other image formats is a must. I've got a few PNGs and GIFs scattered throughout my collection as well. The order in which I mentioned them is totally fine.
3. Does it scan the tags of files for cover art yet? I only see folder.jpg entries in your list, hence my question.
4. Seeing your screenshots I figure it might be useful to be able to sort the list on different criteria too, such as the Cover type column. Does the stand headerclick functionality work?
I'll get around to testing it for myself in ~3 hours, but till then..
Thanks!
Edit: Oh, I just remembered... one program I have used for a while, I think it was WMP? supplied plenty of album art but in a different file format. {GUID}.jpg things I think they were.... ah no, AlbumArt_{5AC5A5E9-9CBD-4D75-B52B-F47B7E452D0A}_Small.jpg and _Large versions respectively. Can you check for those too?