I always add my bg pic in postwork.... its much clearer I find..

Im rendering atm or would check the settings for a bg pic as I cannot remember off the top of my head.

If you do decide to add the bg in postwork, make sure you render on a black bg ( change backgroun colour to black) and save it as a png or a tiff.

"I didn't lose my mind, it was mine to give away"