Why put Mod Podge on top of your photo canvas? The Mod Podge acts not only as a glue but also as a sealer. It will protect your photo's and/or paper and give it a nice finish. Fun Tip: Brush your Mod Podge onto your picture first horizontally and then when dry, reapply vertically to give your picture a "grid-like" canvas texture!
This looks easy enough. I would cover a longer wood piece with fabric to make a multiple hook holder.