First, use the layereffects for a color fillin on the Layer with your White Land. Its looking to plain like this with White.
Second, go to the Layer Effects of your base Mountains and scale the texture of the Stone down by 50%. so you Wong see the obviouse texture so heavily.
Third, go to cgtexture. COM. And grap a handfull of tiled stonetextures and floral textures for the forests.
Forth, have fun