I knocked out a couple billboards from the trading card display protectors I picked up. I glued the protectors to some cheap shaving razor guards to make bases for them. I'm even thinking about gluing them to magnets so I can stick them to metal railings and signpost. I've used parts from these cheap razors in a number of projects.
I found some "Futurist Fashion" images from a quick google search then made a simple logo for the fake fashion design company "Alejandro of Titan" in photoshop. This isn't my most futuristic set of buildings and I know that these ads in particular look a bit out of place but you get the idea.
I printed these out on some luster photo paper then cut them out and slid them into the protectors. I made two "posters" for each billboard. In the future I plan to glue the images together to make them a little easier to deal with and look a little cleaner but These are just test subjects.
One word of warning. You need to be very careful that you keep your work surface clean when using these card display protectors or any other clear plastic items. I messed up one of my heavy duty protectors because I accidentally laid one of the pieces in a small drop of super glue that I got on my work table. I think I can salvage it as a distressed display or I might set it up to be one sided and mount on the side of a building or something.