The majority of our campaigns use different images for mobile and desktop. I'm trying to make this work with retina images, but can't find a fix.

This article talks about using retina - but the fix is to have one image at 1x and one at 2x: https://litmus.com/community/discussions/4931-using-retina-images-as-background-images. This doesn't allow for two different images

This article talks about using 2 versions of retina - but the fix to make it cross-browser compatible means you can't put copy on top of it - hence the desire to use background images: https://litmus.com/community/discussions/5939-mobile-optimised-responsive-fluid-retina-images-for-email

For what it's worth - I've also looked at this article: https://medium.com/inkceptional/fluid-high-resolution-background-images-in-email-5f669577e5b0#.svdzk3htx.

Any help is greatly appreciated!!

Here is what the heros look like as single images

Desktop:

Mobile