Can Rustoleum wood stain bleed through a mounted photograph?
Depending on the type of paper (and more importantly the type of glue you use) the stain will probably attack the paper over a long period of time.

Isolating the stain is a good idea, and I can recommend the following approach. 


First give it a solvent-based coat of transparent varnish. This will protect the stain from the outside world and because of its similar composition will bond to it rather well. Let dry. 
Now give it a water-based coat of transparent varnish, this will enable it to bond with the next two layers. Let dry.
Now use another coat of the water-based varnish and float the photo paper on it. Let dry
Use one last coat of water-based transparent varnish to encapsulate the photo.




A couple words of warning: test the water-based varnish to make sure that it doesn’t damage your photo, watch out for bubbles and always ventilate!