I chose to use 4x4 stone tiles since the look seemed to work well with their travel theme and their logo. You can easily find these in your big box home improvement stores at a very reasonable price.
Also, a very important point is to print them with a laser printer, if you don't the colors will bleed when you apply the transfer medium. For me, I put the image on a thumb drive and took it to my local Staples and printed them there.
Once your images are printed, trim them to the desired size. I used the Mod Podge photo transfer medium. You can find the step-by-step process on their website (which is listed on the back of the bottle).
I chose to leave more of the paper on this project. I liked the way it looked like a piece of an old worn map with the compass component. Based upon how I trimmed the paper and how much of it I removed during the transfer process, no two coasters are exactly the same which was intentional.
I sealed the top of my coasters with three coats of matte Mod Podge making sure to let them dry throughly between coats. Finally, I cut out cork circles and used my hot glue gun to attach them to the bottom of the coasters for a polished finish and eliminate the possibility of any table scratches when they're used.