The diamonds remind me alot of turrican. Actually I just went and had a look at them and theyre pretty different, hehe.
As for recolouring stuff you've done before, I've done that quite alot in the past. Hey if its too good to let go to waste, don't let it go to waste!
A prob I see with this mockup is it comes across more as a sewer than as a dungeon. Maybe it's just me, but when I think of dungeons I think low ceilings, archways, chains and shackles, grunge, rats, corpses/skeletons, barred walls and doors. Just some suggestions for details, I guess.