I saw a Carol Duvall show where they did the same thing only slid the photo onto lamp shades. I don't remember what the solution was, but I'll see if I can find out.
The rocks sound neat!

Here are the instructions for the lamp shade. Maybe you could use the same process to put the photos on rocks?
photo lamp shade

I tried 'something like that' from the Carol Duvall show. The Glossy gel medium was 'clear paint' that was used for painting on glass .You applied a layer or 2 over a color copy - let it dry - then baked it - then "Supposedly" you run it under water and scrape of the paper and you are left with a transparent picture on a sheet of the baked gel medium. Didn't work for me. The picture scraped right off with the paper. I think she was also using these for lampshades and other projects that you need light behind.
It was quite awhile back that I tried it ... hope you have better luck than I did !!! ;)

You could try using water slip decal paper. I think you would need the white paper so the picture would show up on the rock. You print it with your inkjet printer, seal it with clear Krylon, then put the paper in water. THen it slips right off onto whatever you want it on. After it has dried, seal it several times with clear Krylon again.

I always buy my water slip decal paper from ebay.

That's a good idea, GardenGirl. I've used the clear water slip decal paper to put designs on mugs, and used the same process that you did. I also buy my decal paper on Ebay.

What is Krylon? I see it mentioned a lot for sealing different things, but never have been sure what to look for.

Krylon is a brand name. I know they make paint but I guess
from the answer above they make a sealer too.