In spaces prone to dampness, especially bathrooms, Before The Architect (BTA’s) prefers ceramics with a wet (as opposed to the separately determined ‘dry’) COF in the 0.5s.  Less and it can get slippery in BTA’s opinion.  More and it can get tougher and tougher to clean.  In any case, choose the wet COF that suits your needs best.  Otherwise, it’d be natural stones – their preferences: marbles and granites for interior applications. (For exterior applications, porcelain floor tiling seems to be increasing in popularity.)
 

Ceramic tiling in baths is ubiquitous.  Less applied by far is natural stone as a flooring tile.
 

The marbles tend to be less costly than the granites and, with proper application of materials and methods, can perform with integrity.  Marble is soft; lacking a sturdy, evenly supported substrate, marble can crack and breakup. What means ‘sturdy and evenly supported’?  Floor joists: properly sized for live and dead loads on given clearspans and with deflection limits at or better than L/640; solid, full depth braced on 12 linear inch centers; spaced at not greater than 16 linear inches on center; below not less than ¾ linear inch plywood glued and screwed on not greater than 6 linear inch centers.  Above that structure, consider following the prescripts of Laticrete International for finish masonry over wood substrate.  Alternatively, if the application is over masonry substrate – reinforced concrete slab-on-ground, again, consider following the prescripts of Laticrete International for application of finish masonry over masonry substrate. 
 

Some have cautioned to avoid marbles in blacks and greens as being too soft for flooring – tending to fail more easily than lighter colors of marble and tending to bleed sometimes.  Marbles tile flooring come in myriad lighter colors and gorgeous looks.  Marble can be scratched and must be treated with marble cleaning products.
 

Granites tend to have darker looks on average compared to common marbles, and, in BTA’s opinion, are better suited for highlighting either in ground or at perimeters.  Granite is hard – way harder than marble.  While granite floor tile application should mirror that for marbles, be prepared to slow down cutting it in prepping for placement.  Granite can wear down a wet saw blade much more quickly than can marble. 
 

As with a ceiling coffer home ceiling design, symmetry counts especially at perimeters.
 

Please keep the grout lines thinnish, in order to bring out the finish masonry material and limit soiling.