Pebble mosaic tiles
Pebble sheets use rounded, irregular chips rather than a cut geometric shape, so the surface has no repeating grid at all. Both of ours are tumbled marble — Carrara White with Platinum Grey, and Dolomite — where the tumbling does most of the work in softening the edges.
The irregular face and the number of grout lines make pebble one of the better options for a shower floor, where grip matters more than a clean joint. It is more work to fix than a flat mosaic and it wants a flexible adhesive and a decent grout, so it is best kept to small areas where the texture is the point.