Could it be set as an option -- a little check box that says "Exclude folder.jpg from the import" or something like that?
Personally, I've never used the image parts of Media Center for anything except for organizing, renaming, and viewing cover art. And all of my image view schemes and 3d visualizations, etc., are all based around cover art ... so being able to import the folder.jpg files, for me, is kinda critical. When I scan my harddrive that's dedicated to media, I want MC to find everything....
However, I could understand that for people using MC to view their normal picture collections-- stuff other than cover art -- then having all the folder.jpg images mixed in with their family photos or whatever could be annoying.... so an optional filter for them would seem ideal, right?
On the other hand, I'd like to argue for even more folder.jpg support -- primarily, I'd like to see these files dynamically linked with/moved with the audio files. For instance, if I'm in an audio view scheme and I use MC to change the name of an album for a bunch of tracks, and then I choose to rename the files based on the new tags/properties, then all of the tracks get properly moved from the old album folder to a new album folder... and MC asks me if I'd like to delete the old folder since it's empty, and I choose "yes." But if I have a folder.jpg file in that folder, the folder.jpg doesn't get moved to the new album folder (because it's album tag wasn't renamed) and thus the folder isn't empty so MC doesn't ask if the folder should be removed... End result: My media directory has hundreds of album folders that contain only a folder.jpg file and nothing else. It's not the end of the world, mind you, but I thought I should mention it while we're on the folder.jpg subject.
(Note: For my normal image files -- other than cover art -- I'm using ACDSee to organize and view pics, IrfanView for editing/conversion that ACDSee can't handle, and Photoshop for advanced edits... Maybe MC has caught up with or surpassed ACDSee's organization, viewing, and basic edit/convert functionality at this point in time, but, regrettably, I wouldn't know, because I've gotten into such a habit over the years of using the other programs for just for pics and MC just for sound and video ... and cover art. But maybe one day I'll see the light... )