Print out a 3x5 image of whatever you like and cut it out.
Spray the back of the picture with spray adhesive, and stick the switch plate to it.
Fold the edges up around the plate, and snip off the excess, or you can snip off the excess before you even glue it! It's a bit less sticky that way. =)
With an exacto knife, cut an 'x' shape from the front and fold the four little flaps to the back of the plate. They will stick, and thus make room for the actual switch.
Take a pen, and poke a hole in the two little screw holes, again from the front - and viola! Your light plate it done! =)