I made a stencil for my mew reg number the other day and now the bike proudly displays her reg number.
As a bonus, I discovered a quick and easy way of removing waterslide transfers. Simply apply a bit of masking tape and bingo: the transfer on top of numberplate comes away with the tape :scream:
The first lot of transfers I had on my tank lasted until I hosed the mud off the bike. Even a coat of lacquer wouldn't keep them on. They didn't stick to the Matt finish on the tank. I had to go with vinyl decals and lacquered, they work great.