Oh, and then there's GraphicConverter by Thornston Lemke -- slightly more recent than SuperPaint, as it was released in 1992, but unlike SuperPaint, it's still being actively developed today (currently on version 12). And as a bonus, Thornston has made all the "classic" versions freely available - you can still download them from lemkesoft.de today, and he's provided registration codes for them.
I find it awesome that he's been able to keep a shareware product going from 1992 right through 2026 and counting.