All and all a 7.3 or so, Try making the height a LIITTLLEE shorter so the halo dude isn't "Stretched". Also, Throw some more detail into the backround, Like if you want to keep the grid effect then you should probably make the lines a little more dense, Or a neon type of addition like this-
I am not a graphic artist so don't critize me if this is too low. Everything looks good, but the text and the text in the corner looks lout of place. Possibly get a science font so it looks good? Either way, if I could, I'd use that signature.