Place a long bed skirt between your mattress and your box spring. A bed skirt hides the cinder blocks as well as any mess you have under the bed, and it also prevents the area under the bed from getting too dusty. In addition, it softens the harsh edges of your bed frame, giving your room a softer appearance.
Cover the cinder blocks themselves with fabric, disguising their edges and their texture. Wrap the cinder blocks in a cotton print the way that you would a present and secure the fabric with a line of glue. You can change out the fabric as you desire, or you can simply choose a fabric that is a plain color to match the room. A fabric covering also helps protect your floor from scratches.
Cut a wood board that is as wide as the cinderblock and as long as the side of your bed saw. Paint the board or cover it with decorative shelf paper, and then use a pressure-sensitive adhesive putty to affix it to the side of the cinder block. From the side, it simply looks as if your bed is sitting on a pedestal.
Paint the cinder block with acrylic paint. This makes the cinder block into a decorative object, taking away from its clunky appearance. Paint it in a solid color that matches your bedspread or put an artistic design on it.