Hmm yeah it's too small...
And put more decals in! Play with brush forms... There are too much 90° corners. Smooth em so it would look much better.
But the gameplay is nice!
But i found something which is not so nice:
http://xs.to/xs.php?h=xs215&d=07213&f=nexuiz000025.jpg
The floor with the grey metal texture. It's too boring. Put more textures in. And put a different light to items so the player notices: 'Ahh, theres something diferent. I must walk up there!'
Keep your maps up! I am waiting for the next.