Use as a magnet OR a decoration
These are made in a way that they stick flat on your fridge. You can also just sit them on a shelf for decoration. They make great gifts - especially if you use photos.
Use a knife (or other tool) to carve out some holes for the magnets. Make a hole big enough for the magnet to fit in completely. Glue the magnets in, then cover the back of the block with paper (use strong glue!)
Cover the block with decorative paper (or paint it). Glue a picture on the front, and any embellishments you want.