The one thing I noticed, that I notice quite often in custom maps, is that the edges are much too sharp. All the default maps either have:
A. A lip, bevel, or other structural thingy, or...
B. A texture with a noticeable and suitable edge.
Supertanker has too-sharp edges, so does Kaleo, Odin and X-20.
Your face and NOS Brain have it down right in thier shots.