It's ok, but you can improve a few things that will make it look way better
1. the streak of light mention by w000t, it draws to much attention, i agree on that
2. the dark markings on the left ( the +J ) on the sig is useless to be honest

.. you could remove that, doesn't look good
3. if i look closely i see some VERY cool effects, but the entire sig is to blurry and flat, has no depth at all.. try to create more depth.
4. the render is a floating head

.. why can't i see more of her body, i just see her head and shoulder, it makes it look weird

..
those are the things I'd improve on this sig, then it will look allot better, I'm sure
KIU