You can customize the icon that appears next to an asset in the Hypergraph, Hypershade and Outliner. You can either associate all assets of the same template with a common icon or you can mark individual assets with unique icons.
To associate an icon with a template
All asset nodes that use this template are now displayed with this custom icon.
To display a custom icon on a asset
The node for the asset is now displayed with your custom icon.
If the asset you selected is associated with a template that already has an associated icon, then only the selected asset’s icon is changed. The rest of the assets associated with that template are unaffected.
Note that due to the way that the interface handles transparency, you may notice messy borders around the edges of XPM images. To fix this, you must use an image format other than XPM. If you specify XPM, Maya automatically searches for a PNG of the same name before defaulting to XPM.