If you made a lithopane light box from lithophanemaker.com, you could theoretically hold it with this lamp base I made.

You'd have to buy this lamp fixture or something similar, or modify the provided fusion360 file to fit.

Also, you'll notice there is a nice channel for the lamp wire but there isn't enough room for the plug to go through. I cut the wire close to the socket, fed it through the bottom of the holder, and soldered them back together (covered with heat shrink of course). You could also just make the hole on the bottom a lot bigger, but this was a one off so...