Flooring Tile - Can I lay tile on top of other tile?

I want to redo the floor in a bathroom. The current floor is some sort of old tile cut in very small squares. It fits together very well and it is one flat, even surface that has no indentations, or grout line depressions in it at all.

I'd like to install some snap together ceramic tile in this room, but I'm unsure if I need to remove the existing tile first or if I can just tile over it (the height increase does not bother me)

Sure you can lay tile over tile, and yours being the small 1x1 mosaics with plenty of grout line for your thinset to grab is the best case for tile over tile. Use a modified thinset (not premixed) and set your tile after cleaning the original floor of any dirt. You may want to snad the surfce of the tile and grout line with a carbide 40 grit paper first just to abrade the surface some. As for a snap together ceramic floor, given the price/sf with required materials will be about $6 and up per sf and the fact that particleboard substrates (no no in any wet areas) will swell and ruin the job and you could do it for about $3/sf, I'd have to say go with real ceramic. If you do a google search on any of the ceramic snap together floors by the brand name, you will most certainly feel enlightened. Click on consumer responses and not the tons of paid advertisment endorsments from various home improvement web sites introducing these products to the public. These floors have been having some issues with design and are not all they are cracked up to be. "Cracked up" pun intended.