In vue 8 you can create your own terrains. So I think you can generate like forests/mountains etc, and other plants/foliage. So You have a bit more control over what you need rather than relying on photos from the internet. Im not 100% sure. I've seen some nice stuff created with vue, and I've seen lots of terrible stuff too. Im not completely sure of the workflow, I guess there are lots of variations, from rendering out single passes of single objects, to creating a whole environment, and you can import obj files into it aswell. So perhaps you can create a whole image in vue, then tweak in photoshop. Or, as in a tutorial by Chris Stoski on Gnomon I have, you can create just a few trees where you need them, but make and light them exactly to your needs rather than, as I say, rely on google images, or whereever.

Should also help with the matte edges of assets aswell, where say, it can be hard to get a good edge on a tree when cutting it out in Photoshop, with vue, you render out with an alpha and...job done. But like I say, this is largely guesswork on my part. I have bought a comprehensive user guide for vue 8 which is for 3d artists. Am waiting for the transaction to clear on the payment for the software, hopefully a couple of days, then I can put the two together and ... see what happens.