I would rate is 6/10
Reasons:
You can see the white brushing, maybe its for lighting or blending....it is noticible, not good.
There isn't much creativity, it looks like there is a background and you put the render, and just brushed around.
you could improve the sig by:
Maybe add a gradient map.
Add depth to the sig by black and white gradient.
Blend the render more , maybe a little more.
Let some color flow around.
I do not know if i am wrong, but these were some comments by me.