I use reactive targets. ballons, lolipops, cans, soda bottles, old fruit, popper steel targets, dueling trees, hang cans with string like wind chimes, etc.
Birchwood and Casey makes battleship and golf splatter targets games.
Sometimes ill staple an odd shape peice of contruction paper over the center ring of a target and try to group closest to the x.
after easter I take all the eggs and hide them along the range and time my opponent. he resets and hides my targets, then times me.
ive camoflauged fruit out in field with shubs and timed my buddy . he resets for me.
grab some cards from a deck , randomize them together on a copy machine, print it. draw a card, shoot it as fast as you can. for added difficulty: I get a red marker and a nickel and trace a circle in the middle for more points. ive also made random quater and dime ones per each card. 1 pt for card hit , 5 for quater, 10 for dime. -3 points for going over a time limit.
You could paint your steel different colors and arrange them randomly around the range like you mentioned. Then take a deck of candyland cards corresponding to the colors. draw for a 3 targets. shoot them quick.
its also fun to randomize or "draw" your shooting position. (prone, bench, standing etc.)