I have never seen a decent template for OmniGraffle for diagramming individual server computers, user computers, users, network bus/switch, network links, internet cloud/bubble, and so on. Every template I have seen is either too cutesy, oddly missing obvious items, or wildly different sizes and shapes.
I am referring here to the simple case of conceptual sketching, such as for project proposals and situation reviews. I am not talking about network management professionals documenting actual physical networks and computer deployments (that would be nice too, but get the basic simple case fixed first).
P.S. — It’s not obvious from the StencilTown preview, but if you download and install the Home Network stencil you’ll find it also has icons for desktop, laptop, and mobile devices, as well as network-attached storage devices.
It’s a bit light on server options (just the network-attached storage and various networking devices), but some of the other stencils out there (for Amazon Web Services, etc.) do a good job of covering those needs.