Age: You can make "jolly good" pictures with it (see the sample-drawings above and below...), and it's very easy to use. You can only use it for screen 5 drawings, I think that's a pity, but fortunately, some dutch clubs have produced an screen 7 and 8 version (AGE7/AGE8), so you can use the layout of this great program too in the screens 7 and 8 (sounds logically, doesn't it?).
Spen: In this sprite-editor, you can edit sprites in all possible ways, from hardware-sprites to software-sprites, from single-pattern-sprites to multiple-pattern sprites. If you've designed some nice sprites, you can convert them easily into spritedata for ML or Basic. This is THE sprite-design-program for MSX!