1. duplicating the render, off-setting it's position,and setting it to color dodge/burn/etc/etc rarely ever looks good, so do not ever do it (his huge shoulder behind him)
2. there's no light source of the sig, which IMO makes it look LQ/flat. All you really need to do is take a size 200-300 soft brush, create a transparent layer, click ~100 pixels above the top edge of the sig right in the middle.
3. The render looks way too bright compared to the rest of the sig. You could either topaz affect it, or do boubabi's classic light manip technique of making a transparent layer over the render, using a grey colour to completely colour over the render, then setting the layer mode to opacity, and using the BURN and DODGE tools to darken the areas where a shadow would be cast (i.e. under his nose, under his bottom lip, under the helmet, around and under the eye sockets, on his jersey where his head would be blocking the light source) and slightly brighten the parts of the render which the light source is directly shining on.
4. text doesn't fit with the rest of the sig, the bold white sticks out way too much and the color dodged/burned layer over the AVE looks like broken jpg style (way too pixelated, some layer types will cause this, it pretty much needs to be avoided) see the above post for more text info.
5. The shadowing done @ the bottom left/right of the sig is good in theory to create depth, but it's way too black IMO.