When I was in the Military, I met a guy that used to take a picture, and put it on wood, then spread some (two part), epoxy on it, that was clear... Beautiful pictures and wonderful work.
The epoxy was mixed, then poured on the picture and wood, thus sealing in the picture to the wood. I believe in the 70s, they used to do this with professional pictures, because my Mother had one of my brothers and myself made, and to this day they are clear. So you might try this as an alternative.
I dont know what the two part epoxy is, but you could probably go to Ace Hardware, or a True Value Hardware store or some place that deals with that, and inquire...Jesse