Currently the set of supported licensing icons like the ones from CC variants is limited to those of use to Wikimedia Commons. This is limiting to third parties that often allow non-free licenses or more restrictive free licenses (e.g., with "no derivatives" clause). The set of icons shipped with MediaUploader should reflect that. The naming of these icons should be consistent and documented.
Also, currently some of the icons have transparent fills, other white. Some are 18 pixel PNGs like this beautiful specimen, others are SVGs. It should all be SVGs with consistent backgrounds, margins and sizes.