Go on
Welcome to Flickr - Photo Sharing and search their Creative Commons section for "green" or something like that. The Creative Commons images are free for anyone to use as long as you credit the original creator of the work you use and don't make any money from doing so.
If it helps, all of my images at
Flickr: Twentyhertz Likes Videos' Photostream are CC licenced, so you're welcome to use anything you wish as long as I receive a credit and you don't make money from the webpages. Although, I can't think I have anything that might be of any use to you, sorry! hehe.
My advice though... take any plainish photo, open it in photoshop, use the Hue/Saturation tool, click the "Colourise" box, then wiggle the hue control to green, then wiggle the saturation and lightness controls until the image looks suitably faded out.