I second Tim on bringing in some gold on Billy - might make it more natural.
I also think you can play around with the lens flare effect some more. Maybe a more blended and subtle effect would turn out more realistic? And wouldn't it be lighter in the center, more towards pure white, just below his hands?
Great job so far and I'd say you're pretty much finished. Btw, I'm glad you've found a way to bring the slipcase to our custom-community! You have to finish this thread off with a photo of the finished product - slipcase and all.
Samples below, finalized version is uploaded into the gallery.



