The tree fading at the bottom, it just abruptly ends, and fades in a weird spot, I'd say crop that to match the main outline of the signature.
And one thing that is just screaming at me, is the white around the troopers head, and feet.
And maybe level the alien out with the troopers feet, or the outlining edge of the signature.
You don't have to do it, I just needed to get that off my mind.