I think the "How Whonix Works" picture should combine four things into a complicated illustration like Subgraph's.
Effectively, you want to show:
1) Separate host OS (Xen or other)
2) Whonix-WS connecting to a Whonix-GW
3) Whonix-GW choosing random paths through the Tor network with the last step (often) being an unencrypted link - this could be updated to show encrypted connections if .onions
4) Stream isolation
If the illustrator is good enough, they need to combine the following three images below into something sensible. It probably could be a 3d image like Subgraph's to fit it all in.