I am trying to create a skin for ckeditor 4 (well, just custom icons really).
I tried following the skins guide http://docs.ckeditor.com/#!/guide/skin_sdk_intro but annoyingly everything links to the moono skin and says start from there, but there is not even a skin.js file in moono by default. It took me long time to find the source code on github and copy the entire moono skin source folder from the ckeditor-dev reposotiry, and even then, there was not even a default icons.png file.
Anyway, I think i'm all setup now, and have created my skin.js, and I have my icons all in one vertical slot sprite image (copied from a skin i was using on ckeditor 3). The docs say to just call CKEDITOR.skin.addIcon and you'll be good to go. But that method has no effect if the icon you are adding is already set, and in my experience, the stock ckeditor.js file from the standard source already calls addIcon on every possible icon for the moono skin.
All in all I'm finding this process of simply changing the icons ridiculously difficult. At first glance I thought I woud just grab the icons.png file from moono and replace them 1 by 1 in the sprite but even that didn't work. Very frustrating.