These are really so easy to make. Get an inexpensive plastic light switch cover plate. With tacky glue (may have to thin with water a bit) cover the light switch cover plate with a plain coffee filter, generously glued on, making sure to get out all the bubbles, and cutting/poking out the holes
for the switch and the screws. Be sure to overlap on the back side and glue that down well also. Once it's dry then you can paint whatever you'd like on the switch plate cover and it won't rub off with use thanks to the coffee filter. When your design is dry, coat with a varnish or sealant. :) FYI-I like to make sure it's very dry before I
mount it to the wall...or it's almost impossible to take off the wall later.