I think I've discovered how to sketch. I was thinking of a jumping tank with dual rockets/gun turrents. What you see here is the result much erasing and re-penciling. I then colored it in GIMP (much undo/redo). Its not much too look at , but it is my first real pencil sketch ever, and I'm damned proud of it!
Because the game is going to be rendered from the side view, I want to to employ elements of gravity into the game. So there will be arching missles, bombs and jumping rocket-pack mechs, etc. I was thinking this tank could tag the player a bit and make a surprise leap-attack.
This sprite design probably took me much longer to do on paper, than say these using Blender and GIMP, but it was a lot of fun and I can do it anywhere. I might do a few more paper sketches for fun.