Backgrounds for questions

I am wondering if anyone can help me with backgrounds. I have uploaded an image that I am using for background of the first two pages of my survey (through the Look and Feel section). I would then like to upload a different image to be used for the remainder of the questions in my survey. Only problem is, I cannot figure out how to do this. I am currently setting the background of the rest of the survey to white using JavaScript CSS in the questions (see below). As far as I understand, I can only use this code to set the background to a block colour or link to an online image. Any ideas how I can use an image file for the background?

jQuery("#SurveyEngineBody").css({"background":"url('YOUR_IMAGE_URL')",
"background-size": "cover",
"background-repeat": "no-repeat",
" background-position": "center center"});