Maybe it's impossible to do coherent art direction in nebulous volunteer efforts. I don't believe the technology limits the style so much. Certainly that is not the case with something as basic as sounds.
What differs the most from the other Q3-likes (direct clones like OpenArena and more distant ones like Nexuiz) is the core of the game: while the others merely handle framerate-bound physics, bunny hopping, rocket- and strafe-jumping as gameplay side effects, this one is designed from the ground up to integrate such rule-abusive gameplay into its core. Jump features have been added (bounce-jump on walls), physics has been tweaked to provide less hackish strafe jump, configurations options abound to make the game tunable for enthusiasts (like coloring walls and floors instead of simply disabling textures and lightning). It seems this version goes even farther in configurability, with configurable coloring and extensively configurable/scriptable UI.