This is the best thread for a long time!!!!
To the OP, I also have a relatively small man cave, and a reasonably substantial Fleet. Pics will follow, but here's a few starters:
As a general guide, you want to maximise your available floor space in a small area. This means storing as much stuff as possible off the ground eg bike, wheels, spare tyres etc, so you will need to build some stuff to accommodate this. This might sound like Captain Obvious speaking, but don't get into the habit of using your man cave for storing things you don't use very often eg old frames.
Here's my thoughts on some of the things mentioned so far.
Shadow board: -1, especially if you travel with your bike, eg to races. You might want a portable way of organising your tools. I will provide a photo example shortly.
Work bench:For working on bikes, you don't need a wide bench like you do for woodworking. I have three work benches, two of which are only about 400mm deep. Again, photos to follow.