Mopar enclosed trailer decals.

I agree with keeping it plain, or maybe even putting some ford decals on there to deter theft
:poke:

But any local sign shop should work with/for you if you do decide to do something

Have you talked to any of the wrap shops?
The do cars, trucks, busses, RVs, a simple trailer would be peanuts for them, and they will install it for you

Have you ever put up wall paper?
I'd imagine putting up a large decal would be similar and the chances of getting it right the first time may not be great