OP's example is probably some custom adhesive vinyl prints. Probably multiple prints put together even. They could have access to their own large scale vinyl printer somehow, like through a tool library or makerspace.

Once printed, just keep em in tubes, get to the location during some dead hours, and slap em up. Don't need to be perfect, just needs to be good enough to pass a glance.

Wouldn't take but a few seconds, maybe a minute for the larger one. If ya look the part even (safety vest and blue jeans or something similar) then most won't look at you twice to notice what you're doing. Just act with confidence and you're usually golden.