Newer homes will often have a 3/4" subfloor and where vinyl will be laid an additional 1/4" underlayment of smooth plywood to give the vinyl a good adhesion surface.
Dura-ceramic is a hybrid product that can also be grouted.
Other DIY products include Snapstone ceramic tile. This is a product that can be laid over almost any surface. The floor is more forgiving (concerning slope) with this product than traditional ceramic tile. Snap requires NO backer board or mortar. The product sits in plastic trays with rubber feet to keep it from slipping. The trays interlock perfectly aligned with other tiles. Snapstone can then be grouted with their latex-based grout. It is a very durable product. I have used it.
There are a good variety of sizes and colors. There is also another brand name (Avaire?) by the same manufacturer of Snapstone. That offers even more variety in size and colors.
It is not cheap but for a bathroom it would not be a big investment. It has a lower foot print than standard tile with backerboard and mortars, etc.www.snapstone.com