Photography Needed for Texture Artwork

My name is Katy and I work for a game development studio that is looking to get some photographers around the world to take photographs of nature, and other enviromental such things that we would purchase high quality digital copies of to use for creating our own unique texture artwork. We are unsure of how to approach looking for photographers since we're looking for such a "global" look to our game. We also aren't sure what would be considered an appropriate amount for compensation. I would appreciate an insight any one could give me for this project as well as any other sites I could look at to find photographers. These pieces we would want would be close ups of things like grass, bogs, marshes and other landscapes and foliage, that would be used to create a digital texture textile we would paint our worlds with, so we would need royalty free photographs as well. We would pay for the services and such, but we don't want to pay royalties to the photographers for using their photographs as our reference or template for our textures. Thank you for your time and help!!

Katy Fairbanks
Production Assistant
Red 5 Studios
Kfairbanks@red5studios.com

Why not just put out a wants list, say what you're paying, and choose from the submissions you get.