I've done a lot of tile work and love it--in fact, I bought a kiln and handmade tile for my bathroom! But in cases where I wanted to cover up existing tile, but not re-tile, I used a concrete coating over the tile, embossed the patterns I wanted into the concrete, and then stained using acid stain over the concrete. The whole thing then gets coated with waterproof clear coating. I'm new so I can't post pictures yet, but will do it later if you're interested. I know it sounds complicated but it really isn't. The mix for the cement was fairly inexpensive, the stains were inexpensive, too. The most time consuming part was taping off the tub so I wouldn't drip into it. I made a template for embossed areas for my bathroom out of a thin layer of flexible foam (cut it with Hot Wire Foam Factory tools--my husband makes them!
) I did sand castles in my bathroom and sea shells in his. The staining in these didn't come out exactly like I wanted, but I could always do it over again if I want. Anyway, it's an idea for covering old tile that you don't want any longer, and I like it that I can create curved corners so there isn't any place for mold to collect, making it easier to clean.