../ update : and Duplicates
This screenshot is part of my shelf I use when modeling, from left to right: Delete History, Center Pivot, Freeze Transformation, Instance X-1, Instance Y-1 & Instance Z-1 and respective Duplicates too
You can download the icons by "Save Image As.."
Although "FreezeTransform" has a direct icon in Maya, I customize it to better differentiate of "CenterPivot"
Below, Instance Icons and MEL code for each one