Tile replacement can be expensive and laborious. Like the paneling example above, you can paint over tile and completely update the look of your floor. Select a good adhesive latex primer and apply entirely over the clean surface (including the grout). Let dry and cure overnight, and then paint normally with a high-end semi-gloss floor paint.
Create a design with stencils, stamps, sponges, or if your hand is steady, a good brush. If you're experienced, try a faux marble or stone look. Seal with several thin coats of a polyurethane or acrylic sealer and let dry accordingly (not recommended for very high-traffic areas or very wet areas such as showers).