If you have a Hobby Lobby, a Michael's, a Joanne's, or some other type of craft store near you, check there for ceramic paint. There is a paint made to go directly onto already glazed tile. (I'm not sure who makes it, but the brand name "Plaid" is in the back of my mind) After you paint the tile you cure it in your own oven at a low temperature. I cannot say how durable this process is in the long run, but it looks pretty nice. If you're going to use it in an area that doesn't get a lot of wear and tear, it might be perfect.
Also, have you considered painting your own greenware and then having it fired? There are craft stores that specialize in raw tile. You can go there and paint it (or you can buy it there and paint it at home), and then they kiln fire it for you. I don't know what the costs are, but I have a friend that did this for her bathroom shower and it turned out great. It's just as durable as any tile you'd buy at a hardware or decorating store. You might ask at one of the hobby stores mentioned above if they know of a raw ceramics source like this in your area. Good luck, and I hope your creative energy brings you great joy.