If you're just talking about non-portable backup, you might want to get a 250GB external drive (like Acomdata's E5 series) and partition it into two or more areas.
You can use one area for your iBook backup (clone). The other area(s) can be used just for music and/or photo backup.
Of course, if you clone your system, you'll be backing up your photos anyway. But having an extra copy on the other partition means you will be able to restore a prior edit (or the original).
Hope this helps.