I have my own branded number plates carrying the EU logo, with borders and a drop down tab at the bottom with 2 phone numbers and website. Never really thought a lot about it until my mate reckons when he's out trucking, he can pick out one of my cars from about 50 metres away. Apparently something about them is quite distinct, which cant be a bad thing. Whether they will be as distinct without the EU logo post Brexit I'm not so sure!
Also rear window stickers, nothing fancy, but I always thought they are quite important. Gives the car behind something to read when stuck in traffic! To be fair, I think key fobs are a waste of time. They only advertise to those who already bought from you.