How do i make my texturses look more real and how do i put mountains or other stuff in the background?
I am not sure what you mean by more realistic??? The textures are going to look like they do in the game as long as you do not size them larger than what they were intended to be. Also alot of the realism is going to come from how you light the level. you can add mountains in the back ground using terragen.. www.planetpointy for a tutorial
you can also add them useing a props_skyportal just like they did in the escape map. if you want you can just copy the portal box from the escape map and drop it in your map.