Adding images to RISE sorting activity

I used a custom background that I created to show an image under each of the for answer options. It looked pretty good!

HOWEVER--- when you access the course via a mobile device, everything is skewed (you can only see two items from my custom background image and they are not lined up with their respective answer options).

So this is only a possible option for anyone who is confident that the course will only be accessed on a computer where the answer options are laid out four in a row (1x4) instead of on a mobile device where they are laid out 2x2. 

(Presumably different display settings could mess with this as well, as might accessibility be an issue due to four images registering as a single image).

Here's hoping there is progress on this soon. I would rather this simple feature be available before adding fancy extravagancies.