Footer Sidebar Area Background Image on Parallax theme

Hi, I used the free version of the Parallax Frame theme for a while and now upgraded to the pro version. Now I run into the problem that I cannot find where to change the picture of "Footer Sidebar Area Background Image". It used to be (in the free theme) under Background Image, but now it's not there. I have looked through all the settings but can't find it, probably my mistake, but I would love if someone could point me in the right direction. Now I just hardcoded changed the image "supplementary-bg.jpg" in the \wp-content\themes\parallax-frame\images\gallery\ to the image I want... Kind Regards Pierre