Extend
If you don't like the glyph icons we have used or our logic in terms of when specific glyph applies you can simply edit the _vs2012.intallisense.js file.
You can find some help about how the intellisense work in VS2012 here
There is an old article back in VS2010 about __namespace, __enum and __class here. We do support both __XXXX and _isXXXX aliases e.g _isNamespace, _isEnum, _isClass, _isInterface, _isEvent, _isMap.
Doing some cool fixes or enhancements please send us a pull request too!