Hmm, this is one of the most interesting wallpapers I've seen in quite a while, so here goes...I notice a faint outer glow on the character, which isn't so bad because it doesn't cover up any extraction problems, if any are present, and it's not as noticable to many other members. The moon could use both an outer and an inner glow so it has a shine and it will look like it wasn't just slapped there, and in addition, the sky could be just a bit brighter around the area of the moon. The stars are kind of cluttered, so maybe you should decrease the number of stars that are showing on the star field.
Lastly, the scan could go for a smoother look, meaning that you could use a bit of a cleaning tutorial. Duplicate the scan layer 3 times and hide the original layer. On copy 1, use a gaussian blur of 1.5 and control click on the original layer to highlight the selection. Then invert the selection and delete it from the layer you used the gaussian blur on to remove the excess. On copy 2, use a Smart Blur of radius 11, threshold 35, and high quality. On copy 3, switch the blending mode to Darken and adjust the opacity of that layer accordingly. You should have a cleaner and smoother appearance for the scan. Don't forget to link all the scan layers in the event you need to move them.
