Managed to get the paper peeled from the acrylic gel medium and adhere these first test images to a couple of three-inch wooden squares before leaving for work this morning.
Pretty psyched about the results. The commissioned works will use four-inch ceramic tiles in a vanilla hue and probably be a touch less grungy looking than these. I do like that you can see the wood grain as part of the resulting image here, though.
Looking forward to comparing the water slide decal method with this process.