Okay first no dark colors second for your bathroom floor use a tile but make sure it has texture to it for safety theres some new 5x12 rectangle at home depot and make sure to use a top brand sealer

You can install an underfloor heating system which is a series of pipes running under the floor where hot water runs and creates a warm floor and also heats the room with radiant heat. This is actually the most effective form of heating a space and is the most comfortable. The system components can be purchased or you can have a licensed contractor install it for you. You can put just about any type of flooring over the top......tile, laminate wood,........ Regarding flooring, if it is a very wet bathroom, I would prefer tile, but if will not get a lot of moisture you can use wood or laminate flooring.

I wouldn't put any water under there because of potential mould issues (in fact, there looks like there's a bit of mould already -- is there?). You could tile the bottom of it and put a strip of LED lights under the glass. What did you have in mind when you initially thought of the idea?

We need a lot more info