I took your pictures to Micheals to get a quote on framing it... just a metal frame... And they want $140.oo *PER* photo. No offense, but for the garage, eff that.
I wanted a mechanical feel too it, so; - couple sticks of metal conduit (~$3.00 per 8 feet) - 4x 90' corners (~9.00 for 4) - some plexi (~ varied $10-$30) - Misc Screws (~ 1.00) - conduit c-clamps reformed to help float the picture (~ 4.00)