How can I set my background images to CSS sprites?

I have about 10 small pic’s which are really slowing down my site and all come from my theme’s background. I am trying to convert these all into a single sprite sheet. I have used sprite’s before on images I post, but I’m having difficulty forcing the automatically loaded background images to load from a sprite sheet.

Basically, all I need to do is change the file path where the background images are loaded from into one common file, but I’m not sure where this file resides. I’m pretty sure I could figure it out from there.

My site (under development) is https://new.renaissanceeuropeanspa.com/.

Thanks in advance for the help ~