Here's a site for you to start looking. http://www.pcgameshardware.com/aid,677070/Texture-mods-for-Flight-Simulator-X-deliver-photorealistic-graphics/News/
Normally when I want to change something, I turn to the all mighty
Google search engine. I suggest ya start with FSX ( Or Flight Simulator ) enviroment mods. There are usually tons of free, quality, mods floating around on that there inter-web. So go out there and start searching!