just because a sig is meant to be dark doesnt mean it has to look boring. different shades of dark :P
try adding some foreground effects that arent as dark as the bg and some effects behind the focal that arent as dark, just to make it pop more. plus a bit of light to brighten up the focal amongst the darkness is a good idea. if people are critiqing your sig saying its too dark, dont reply with 'its meant to be dark', otherwise youll never learn. Id say this sig is too dark and, no offense, but unfinished.
hard for me to critique when I dont know how long youve been making sigs for though. how long? :O