Basics.
^Scanlines.
^Combining pictures.
^Changing backgrounds.
^Overlaying.
Don't try to call paint a bad program. It can be good. If you have endless amounts of time.
(Yes, you're competing with that if you become a teacher.
)
Anyways, first person answered your question methinks. Go to that thread, PM the mod in charge of it all, and keep your fingers crossed.
Go Paint!