I have a 3/4 size one which i cannot remember the size of but looks tiny compared to a standard plate, but looks really good on the car and i've never been pulled. Try fancy plates.com for lots of different designs
I've got a 12 inch plate on the front - looks much better than the standard size plate!
Keep a standard front plate at home though, and attach the plate to the front of the car with heavy duty Velcro - Mr. Plod can easily be appeased if necessary!