A new release of Quick Sprites is being published on the Mac App Store and will be shortly available for everyone.
Version 1.9 enables you to create sprite sheets with different versions of the same sprite: one for normal users and one that will be seen only on Retina displays. It’s as easy as importing the two images in the proper size (the Retina one should be 2x on each dimension) and ticking a checkbox: 🙂
Setting the Retina flag on a sprite means that it’s a version that should be used only by Retina display users. In this case, make sure you have also added a smaller image for normal users, using the same selector.
In some cases, it might be worth creating two documents: one with the normal sprites and one with only the Retina display overrides, so that normal users won’t have to download the higher resolution graphics. Remember to load both style sheets in your HTML page: first the normal one, then the one for Retina users.