my sugestion for do9 show thumbnails in tooltip for files and folders (folder.jpg) in normal, detail etc. view (for 'mouse over' files/folders). of course with any other file/folder descriptions.
it could be great for album art (folder.jpg) or when you dont want load all thumbnails (its slowly then show one thumbnail in tooltip)
Go to Settings -> File Types, and edit the filetypes you want, adding {thumbnail} on the InfoTip tab.
The All Folders and All Files filetypes are good places to start, since most things inherit their InfoTips from them, while for music files like WMA you should edit the Music filetype group.