I like the original artwork you did via photoshop painting. If you already put 14 hours into that, I think the background is worth doing on your own too. It would help pull the piece together as a whole and look more unified. PLUS it would be all original artwork at that point, which, in my opinion, is something to be a little more proud of then just using the asset pack. In my opinion, the asset pack background looks like it was just thrown in there. Hope that helps! Good luck!