Dell customization of the image includes: What drivers and files are modified or included on the Dell EMC Customized Image of VMware ESXi? Each image is a customization of the base VMware image of a particular version.
To determine if your server requires the DellEMC Customized Image of VMware ESXi, see ESXi 6.x Image Customization Information. Certain Dell PowerEdge servers require the use of the Dell EMC Customized Image of VMware ESXi for the easiest and most reliable deployment of a fully managed server.