There are many operators and other interface element across the board that need either updated icons or new icons entirely. Often this is due to duplicate usage of the same icon (such as Render and OpenGL Render).
This is a parent task to begin collecting tasks for necessary icon updates.
Note: we do not currently have an icon designer that's available, and so I've set this to low priority until we're able to give it some real attention. If you wish to take a shot at icons feel free to submit patches for review.