I started using Visual Studio 2015 since a couple of months and just noticed that the Icon Editor is missing!!! In previous versions' of Visual Studio I always used the Image Editor for editing icons, but in 2015 I can't find it and, if I double click on an icon file it opens the Paint.
Maybe I forgot something on the installation or did Microsoft remove it from Visual Studio?
Did you install C++? I had the same problem, but was resolved after installing