I have a bit of a problem in that I want a modern looking building but with very few buildings being available outside of engine sheds or "print yourself", I've made this:

The idea is simple - a 3 sided box with a lid, a window and set of glass doors. I've also added some supporting girders and some taller girders for a sloped roof that I'll be putting on top later this week.

The last thing will be I'll paint the roof a dark black and perhaps a second grey coat on the walls.