This post has an example and descriptions on creating a submenu off the context menu:
[Set File & Folder Colors/Labels via Context Menu)
The Images toolbar is part of the default config and has rotate buttons on it (and lets you rotate lots of images with less clicking) but I'm not sure if the rotation options were ever part of the default config. If they are they don't seem to be now.
If you're using multiple machines you can always export/import all or part of your configuration.