BobVila.com

Mosaic size tiles are just fine on floors, but I think it's going to depend on the type of tile you're using -- I would ask the manufacturer or distributor whether the tile is designed for or deemed strong enough for use on floors. Whenever we purchase tile for DIY work, we've been told that stuff designated/marketed as "wall tile" isn't up to specs to withstand floor application.

Having said that, we put a marble mosaic down on our bathroom floor very successfully, despite having concerns about whether it would hold up. We did use extra care --we put in a solid subfloor w/ a latex-additive thinset between plywood and backerboard, and we used an epoxy thinset to adhere the tile. It's probably overkill but we decided it was worth it. If you went through the trouble of making your own design, you probably want the job the best chance of surviving as long as possible...