I love the background here. It's fantastic. Render effects are good as well. It's definitely one of your best artworks. I guess you reserve your best for collabs. The one you managed with Gazza was brilliant and now this. It's heaps better than the other things I find here.
Now for some criticism, the render looks low quality. A quality render (like the one you managed in the Djokovic sig) can prove wonders for the artwork, whereas at the same time a low quality render can spoil a well made artwork. The second thing I've noticed in your artworks is the 'poor' style of blending. You gotta learn that for blending a render into the background you don't always have to brighten the area around it. A coupe of soft brushes/few textures over the render can seal the deal as well.