Feature summary (what you would like to be able to do and where):
If i do something like background-image: url( 'https://upload.wikimedia.org/wikipedia/commons/thumb/...' ); have it register that the image being referenced is being used by the TemplateStyles page
Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
Would allow commons admins to know if and where a specific image is being used.