Best way to make cinder block walls look good what works if I want to

you can paint them

Paint textured paint on it - the thicker the better. Will make the wall look like stucco.

You can also do faux finishing. Paint the walls with semi gloss plaint such as white, let dry, brush on & tap off with a ball of cheesecloth, a gray glaze mixture. (1 part gray paint, 3 parts clear glaze). You can also do two tone colors, dark green over mint green, mocha glaze over cream, black glaze over bright orange for a leather look. Sounds terrible, but when it dries it will look amazing. Remember to keep a 'wet' edge when smudging with cheesecloth. (Tap the wet edges first and do not overlap.) Test it out on old cardboard first to see if this is something you would like. It's fun and very creative. YOU CAN DO IT!!!!!

You can use this Kilz Hide-All primer that will smooth out the walls, and then paint with your paint of choice.... http://www.kilz.com/primer/kilz-hide-all

You could hang a big rug on top of the cinder blocks. Use a masonry bit in your screwdriver to drill holes in the cinder block. You could put up a rod to hang the rug from. No painting involved.