You are off to a good start in that you have some of the elements needed to make something look 3d -like shadows - and that it tiles.

A few more tips to try next.

-As slacer said a common mistake some make is when creating the stone surface they use one large texture so you'll have something like individual bricks but a line, color or light of dark area of the stones surface that travels across several bricks making it obvious that one texture was layed on top. You'll can try several similar textures, or pick different areas of the surface texture and map them to different bricks, or paint over them by hand a little so these patterns aren't viewable.

-The edges or the bricks are too sharp and even you can try using small push, burn and dodge or even eraser with some sort of grunge brush to roughen the edges.

-If you saved the selection of the mortar area -or can select it by playing with the magic wand- you might try a coarser cement texture between the bricks and also darken the grout by lowering the gamma for example; our eyes percieve stuff that is brighter as 'closer.' It is unlikely that the grout which is shadowed by the bricks would be brighter than them.

Anyway good luck, you've made a nice start.