We have gone through many texture styles trying to find something that looks good and is easy to accomplish. We starting with using realistic and photo textures from sites online, But this runs into problems with credits.
We next tried to use ones with open source licenses and running them theough a photoshop like a previous way i had done before, http://blog.kennyist.com/?p=842 , and trying to create many styles from one picture but it never came out looking good in game.
We ended up making textures from scratch using a cartoony painting type look that creates something that looks great without too much effort, for example:
Once we had a style set, To keep track of what was being produced I started a Google drive like so: