Being a fan of concept art a have many books for games and films.
Most relevant to this project would be my fable 2 art book
I think one of the things i choose this as one of my images to use in research was because of its use of scratchy lines yet this was one of the finalized concepts for the game, i think it also appealed to me as quite a lot of my concepts have a scratchy look about them. When looked at closely you can also see simplistic the detail is in the image yet is still gives the impression of detail by letting your brain filling the gap.
I also thought the to images at the bottom were relevant as the group wanted to animate the changing of seasons in our final project. i liked the way that you can show changing of season simply by changing the colour palette.
Obviously in my own concepts i wont try and copy the style but these are a few examples of similar concept art