I think that artwork could at least start with a simple link that says "additional images" (hidden if there aren't any). When clicked just open an image gallery window showing whatever supported image formats you choose... click image for larger view. There are many plugin routines available for images scaling around. (possibly allow linking to a picture viewer of their choice like picassa if installed)

Let the user create and populate this folder with anything they want. I might include pdf as a supported file along with the usual jpg, png bmp etc.

I would say that where this folder was could be handled the same way it is done for locating the actual files for playing. just provide a way for the user to point to a folder of their choice.

Leave more sophisticated integration for later versions.

Just a thought.

Fred