Time to get back to work. I'm making some robots next. Will probably upload by Sunday.
In concept art, three things guide your decisions when making shapes: appeal, functionality and gameplay implications.
A lot of hard surface and architecture design is about adjusting angles to make straight lines flow in a nice way.
In the same way that you want to distribute polycount and texture space, you want to put your detail on the part that is most exposed to the camera, or position your concept so that the biggest area of importance is seen.
The way you usually tell a professional from a student is by spotting shortcuts in brushwork. A student, while perhaps having the same skill as a professional, will not have had enough experience to simplify his painting process into something efficient and effortless.
When you don't want to design new shapes, guide the eye with dust, scratches and other texture details.
I heard this new rumour that Diablo III is actually set in Mexico.