Hi Doug,
Beautiful Work!!!!! Many thanks for sharing your creations.
I make some of these but not in the real 3D like your examples.
I drill a couple of holes near the bottom and utilize a couple pieces of 1/2" 6061T6 Aluminum rods with one end drilled and tapped to accept a 10/32 round head button screw to support it like a picture frame. I bead blast the aluminum rods to give them a nice finish. I have a friend in California that makes the LED Strips that do a good job in hiding the LED's. I have also done some of them with mirrored Plexiglas. These work better when you add a clock as it hides the clock mechanism and only the numbers and associated artwork show. With my mounting system you can either sit them on the table like a standard picture or flip the mounting system upside down and hang them from chains from the ceiling or wall mount them. You can even apply paint to the reverse side of the mirrored plexiglas to add color when the sign is not lit. It still lights up but not as effective.
Just thought I would share. I have had a lot of fun experimenting with LED's. It is amazing how far those LED's will transmit light. I recently made one (not 3D) that was 24 inches tall and 36 inches wide and the lighting worked quite well.
John