Yes, But not on the N900 that easily...

What PeterPopper said^. Use a program on your desktop computer to edit tags.

Change the "Album" tag to whatever you like (and you can also use your own image) and they will all appear in that same "album" sub-folder.

Change the "Album Artist" tag to whatever you like and these sub-folders will appear under one main folder.

If you use a mass editor like TagScanner 5.1.563, you can change all of this in one fell swoop.