Okay, I have what I hope is helpful constructive criticism.  I don't think your problem rests in it being too dark but I have a list of things that are popping out at me.  They may seem harsh, so if you want, let me know if you want a private email, or to let her rip in here if you want it.  Mind you, this is coming from what I would do with this image for my personal style, which is not neccessarily yours.  So any suggestions/criticism I have should be taken as such and/or rejected as such, and are in the interest of giving you options to make your art better from my point of view. :c)

mdb