So in the latest issue, Wil Overton gives the folowing advice to artists looking to break into the gaming industry: he basically says that diversity is key, that he sees alot of applications that have "... the spark of talent there, but haven't got the breadth of subject matter. You need to be able to draw anything you can think of. People come in thinking they'll be able to draw monsters and space marines, but that's not the case..."
So my question is: what should my portfolio consist of, in terms of conceptual art? Should I have pieces depicting lampposts, trash cans, telephones, and other mundane subjects? How can I prove to them that I can draw anything, while also showing off my imagination and style?
Basically, what types of pieces consist a strong portfolio?
Also, this quote and question are in regards to concept art, but do they also apply to book illustration?