I think this website should add landscape and urban areas i.e.-fields, buildings, architecture, etc. Even though it doesn't conform to the usual subjects on this site, it still would show the flow, the"line of action" so to say. Plus, it allows us to study the fundamentals in recognizing shapes and lighting, which is crucial in art.
We started building such a tool about... oh, three years ago, but faced challenges that stopped it from ever quite being released.
I can't say anything definite, but I would suggest that you might look for new life in that project as more new features roll out after our new site release in September... You didn't hear it from me! ;)