In the semi-official Rust lore that exists in my brain (and the secret Lore Trello), the map below is generated by implants in the Newman's brains. As they roam the island, what they see is uploaded to ISS. The dead station, half-destroyed by a zombie Sandra Bullock, generates the image and sends it to the planet Oxide, where Rust is the #1 TV show. What I'm saying is that you're all stars.
How it really works is more prosaic: any server running the
Oxide 2 Modding API can generate an image of their world with
this map plug-in. You can stare at the flattened peaks and valleys of your map seed, and even add features like rad zones and monuments. Sadly, player buildings are not supported. If you want players to know what they're getting into when they join the map, you can add it to your website like
Rustified does.
But there's an even easier way to generate a map. Fansite
PlayrustHQ has set it up so you can enter the seed and size of the world into their site, and it'll generate a map. The map above was made using their site with the seed 5138008, which is officially the world's funniest number.