Mac installation: 
Get info on folder, select icon in Info panel, copy and then get info on Maya app and paste the icon over the existing icon. This method lets you delete the icon and revert to the default if you want to.  

Linux installation:
Replace maya icon PNG (mayaico.png) in /usr/autodesk/maya201x-64/resources/ via sudo cp terminal command

Windows installation: 
Get info on the application shortcut and replace the icon in the icon settings.