If you have a wall to spare, a shelving system can make for a great custom workspace. This one is filled with stuff, but still manages to look bright and organised.
One interesting feature of this workspace, compared to other shelf wprkspaces is the desk is set perpendicular to the shelves, so working there should feel more open than when facing a wall. Here's another angle of this modern apartment's home office space featured on Home Designing:
Converted Industrial Space Becomes a Pretty, Sunny Apartment [Home Designing]