I found a product called Luma Vue on Costco.com that seems to be a really great way to advertise in your store, and it is really pretty cheap as well. They are LED backlit frames with custom printing, the 18x24 model runs about $230 with your artwork prited on it, and it looks like down the road if you want a new image printed it is around $30. It could even be used as a menu if you could figure out a way to deal with price changes. On the Luma Vue website they have a write on version as well and maybe that would work perfect. I just though I would pass this on and hopefully it works for someone on here. Good luck!
I just saw these in use at Yogurtland. They look great, but obviously with professional artwork. The key is figuring out what the sheets cost. I’m sure you can get them done anywhere that prints transluscent sheets.