[tbworld]

What you are referring too is a sprite located at 'clientscript/ckeditor/images/icons.png'. I doubt there is a higher resolution sprite available. It is something you will probably have to make up yourself.

You can add individual icons to the ckeditor via the ckeditor plugin system. There are several articles on vBulletin.org, on how to add an icon to a CKeditor plugin.
Hopefully, someone else can give you a better solution.

Check the CKeditor forum on their site -- maybe you can find something there, although a Google search turned up nothing useful.