It's fun to carve your own stamps, and it's easy when you use inexpensive erasers for the carving material. Novelty erasers have designs printed on them, come in fun shapes, and can be found in the dollar store. Just follow the printed design to carve a stamp.
If the image printed on the eraser is complicated, simplify it by carving only the main shapes. What is carved away will not print, and what is left will print. Start with something simple. It isn't necessary to carve very deep. If you mess up, just start with a new eraser.