Well, WIP L4D shots I've seen usually look less "eyecandy" than Crysis or Unreal, though by no means bad. It's just that a lot of people tend to build a couple boxes with orange textures, then slap brick textures on and scatter broken cars all around.
> It's harder to find resources based around demonstrating the design side over just pretty things.
Yeah, it seems so.
I can only suggest looking into neighboring categories of games, such as platformers, RPGs etc and trying to find what makes them interesting. I myself am making it a point recently to play major titles from the recent years and analyze them. Since established mechanics in FPS are kinda worn out - escort the NPC, defend the camp, collect X items, kill X enemies, etc - looking into other games can be inspiring. Nothing against established mechanics, if they're pulled off solidly - but if something's old, I wanna put a little shine on it...
I am guilty of shamelessly stealing from Tomb Raider: Anniversary when it comes to traps - that game is like a trap constructor's manual and many elements can be transferred to Quake for example (and still work).
Reading this thread at quakeone.com:
http://quakeone.com/forums/quake-talk/chat-o-rama/6276-you-find-yourself-e1m1.html
I was thinking it could be insanely cool if you could really construct new weapons in an FPS by finding a broken rocket launcher and combining it with, say, an explobox and batteries to create a flame thrower... if you could really make that feel as if you had freedom in constructing things.
U-Invent machines come to mind.