I discovered an interesting feature today. I always thought that CRM stored custom icons in the inetpub folder. However it turns out that the custom entity icons are stored in the database (in the form xml).

 

        <Icon type="GridIcon">R0lGODlhEAAQANUzAP//s9nYh7+/fc/Pj9CkG9TJe//3n8+iG//xl/TQcPXsqc/HfM/PhP/+4///9f/Vcf/90tnZpc/Kf7+/if/8vcTEj9nZl//qjenLcdnZiP/de//6pNTFd8nJi9TPgf/Qat/fqunYftCkF//WcKmpc//geru5rP/9l//Ra//1j//uiNmmGv/ogv//8v//33l3a9KkEv//mf//zP///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACH5BAEAADMALAAAAAAQABAAAAaNwJlwSCwKYcikUmmawRytqHTagr2cDZd2y3VZnRCZODKpgMTiL4wCAHRIgwHJ0gaoN7EYI5MXCPIxagYnhIQBJAGFaggpjSkSJB6OKWoXKpcqJAuYl2osn58FIaCfaholqCUkHKhKVzAPI7IjGAmyMAoEL00wHyi/wL8wIrtHK8fIyAfFQiYvz9DRTUJBADs=</Icon>

      </Icons>

 

These are then rendered with an aspx page which takes the encoded image from the database and displays it as an image (naturally these are also cached for performance). All the 'application' icons are stored in the file system.

 

The good news here is: when moving between different implementations - your icons will come over with the ImportExport.xml and you don't have to worry about deploying custom icons out to load balanced servers.