We've tested a number of materials and the board that works best is board made of cotton with the graphics uv printed directly onto it. We tried adhering a sticker, photograph, paper, etc to a thick cardstock and everything delaminates with the oils. We printed directly onto the thick cardstock as well and just smelled like a wet box and vanilla. That cotton board also has to be die-cut, we could not get a decent cut on our Zund with any knife.
I think the best route is to sublimate them if you are capable. You can buy an assortment of various shapes from amazon.