Thanks for your question. It’s possible to set two images in cd-half-block left-side as background image. For this you need to set the background url like this:
background-image: url(example.png), url(example.png);
background-position: left top, right bottom, left top; (You have to set this on your way)
If you want to use 3 images then set like this:
background: url(example.png) left top no-repeat, url(example.png) right bottom no-repeat, url(example.jpg) left top no-repeat;
Hope this will help you for solve your problem.
In Left block there is by default 1 background image, if you want to add another background image in right block follow the same rule reply to you before. For this you need to set only one image url as background image.