They can do anything you like! Go onto the fancyplates website and create the look you like, with the border, flags, font etc all to your liking. When you then submit that and go onto the next page you have the chance to chose what size you want.
I'm sure there is a 3/4 size option in the drop down box, so pick that if that's the size you want. Or, as I did, you can enter your own measurements. I wanted the plate to be the exact size of the plate holder on the bumper, so I got those measurements and entered them into the FP website and bingo, job done