We selected 12x12 scrapbook paper & cut the paper to fit. I coated the boards in Mod Podge & attached the paper. Once this is dry you can sand down the excess paper on the edges. The finished product looks like this... (apologies for the lil boy foot, he thought these were stepping stones)
These will hang on their walls & I plan to display their artwork above it. The best thing about it is this was under $10 start to finish.