Dynamic Background Images (by page)

Hello everyone!

I’m developing a very simple theme and I’ve a design problem. I’ve many Pages and every single page should have an own full scaled background image (So it should be the background of the whole page).
Of course, it’s easy to write it in the style.css body as cover-sized. But that’s not dynamically, I think. It’s not important, that it’s easy to change.

My first thought was:
Check the page ID in big if/else loop and set the image in body style by jQuery.

So, what’s your opinion on how to implement such dynamic background images?

Thank’s for reading,
Jan