Please submit a pull request if you'd like to use Shields badges for a project that isn't yet supported, I'll gladly add them to the repository.
See the issue where we discuss solutions to build and implement Retina-ready badges. We need help updating all existing badges to support @2x resolution.
Our long term goal is to transform Shields into a service with which widely compatible badges can be generated via a simple API call, any help with this would be much appreciated.
Thanks, @olivierlacan