After a lot of research I found that there are many ways get pictures onto stone, each with varying effects. I tried out three methods and eventually went with one though I will talk about the the other two as well.
Step 1: Materials
For the photo, vibrant colors will of course show up better and it's a good idea to use a big picture with simple details. Regular photographs don't work very well; photocopies are best, or you can print them off of your computer (Lazer is best but ink jet will work too, you just have to be more careful because it's prone to smearing). If your picture has words be sure to flip the image because the end result will me a mirror image of the original picture.
For the object being transferred onto, I obviously choose some thin slabs of stone, but there are many other things you can use if you don't have any stone or don't like it. You can use wood, fabric, most kinds of plastic, or metal. Whatever you use be sure it's clean and as smooth as possible; you can see in the pictures that the stone I used isn't prefectly smooth- that's ok, it just means more work.
For the transfer medium there are many options. The cheapest I found is xylene; it's sold in quart or gallon sized containers at hardware stores and will cost around $10 or less and the process is quick and simple. All you need to do is place the image face down on whatever you are transferring to, brush the xylene on, and burnish well. Repeat this process as needed (between 3 and 5 times). The down side is that this chemical requires lots of burnishing (vigorous rubbing to get the image to transfer) and doesn't produce a very crisp image. It's good for achieving an old or weathered look and works well on fabric but is not good for stone.
The best I found was gel medium. There are a few brands but the one I used was liquitex; this requires little burnishing and it dries clear so it's good for transferring text bit it is more expensive, an 8oz bottle cost me $12 and you have to brush it on kind of thick.
The method I ended up using was mod podge transfer medium. 8oz cost me $6 and it is still decent quality and easy to use. It requires moderate burnishing and produces a good quality picture. However, it does not dry clear, so if you are transferring text only you will end up with a white background.
As I said before there are other methods but these are the ones I tried out, feel free to experiment with others though since each one produces a slightly different look.
Step 2: Put It Together
Get your picture ready by trimming any edges and positioning it so you know it will fit and look good (keep in mind that it will be a mirror image of what you have now).
Brush the transfer medium onto the face of the picture. If you are transferring onto a rough surface then brush done on that too so that it kind of smoothes it out a little. You can see in the pictures that I didn't go all the way to the edges of the picture, that's because I wanted a more natural looking edge; if you prefer straight lines then go all the way to the edge of the picture.
Carefully place the picture face down on the stone (or whatever you are using)and rub going from the center out to release bubbles and to get it to stick evenly. Now you need to burnish the image; many people use the back of a spoon for this part, but since I was transferring onto stone which had a couple of sharp spots I used my fingers to avoid tearing through the paper, this also makes it easier to get into cracks and ridges. When you are satisfied, take a damp cloth and lightly blot over the paper until you can see the picture through it. Now all you have to do is wait for it to dry (the transfer medium, not the water) this will take 8 to 24 hours.
Step 3: Reveal the Picture
When all the paper is removed you can either brush or spray a protective clear coat on the image or leave it as is. Now you are ready to display your pictures or give them away as unique and personal gifts. Thanks for reading!