Make sure it doesn't obscure the state name.
I was pulled over last month because I had the Mickey, Goofy, etc., 'Been there, Done that, Going back" frame on and you could not clearly see the state. The State Trooper was very nice and said, "I don't know what the law is in FL, but here in Maryland, we need to be able to read the state name." He checked my record and just gave me a written warning. As soon as I got home, DH took off the frame and tossed it. I loved it, but it's not worth a ticket.
My sister did get a ticket for hers, but to be honest, she was actually stopped for speeding and the trooper gave her the lesser of the two tickets he could have given her. She was running late and was rushing to the hospital in PA to be with our other sister who was having her kidney removed, so he gave her a break. $56, so she took her frame right off as well.
On our way down here to FL, we saw many cars with dealer's and other cute frames all obscuring the state name. We were thinking that in the old days when each state had a unique plate, it was easy to tell where the car was from, but nowadays each state has so many different options, you really have no idea what state it is. I always read out to DH "Florida, Tennessee, New Jersey, etc." This time it was "Florida, no idea, Massachusetts, no idea, no idea, etc."