Go to www.thepernproject.com and go download the source to StaringMonkey''s things. I don''t know if he has a site or anything, but you can download the stuff there. It''s not exactly a tutorial, and it is usually in mode 0, but that will show you everything you need to know about a non-rotation background. As far as the rotation backgrounds, take a look at Dovoto''s (the owner of the pern project site)
You may have already seen the site, but its the best I can seem to find. StaringMonkey''s code just makes more sense to me, but that might just be me. As far as Mode 3... Sorry... I can''t think of anything off the top of my head. If nothing else, go to gbadev.org, and look for any demos that have source. Hope I''ve been of at least a little help.