I made this Mosaic of his Equestria Pen and Paper RPG character Graystan for Carnorius for his recent birthday. It is based on this vector.  
There are several more images of the making of this mosaic:  
To create such a mosaic the outlines of the image are glued (with a special glue for the stones) onto a net and afterwards the outlines are filled in with more stones. When all the stones are glued onto the net, the parts of the net not covered by stones can be cut around and the whol think can be moved around (and turned) freely. Later the net with the mosaic is glued onto a background which previously has to be treated with a special primer to allow for the net and the stones to stick to the background. Later on the gaps between the stones can (but needn’t be) filled with grout. In case of this mosaic I used grout only between the gray stones but not between the other colors where it might have looked somewhat messy.