Why do images exist of the unbuilt G3 battlecruisers?

Where do pictures of the never-built G3 battlecruisers come from?

They are kit-bashed or 3D-modelled reconstructions based on the designs.

A viewer notices images of ships that were never constructed and asks how apparent photographs can exist. Kit-bashing and 3D modelling allow artists and historians to visualize the planned G3 battlecruisers from surviving design material. The images are reconstructions rather than evidence that a hull reached completion. They distinguish modern visual interpretation from the historical construction record.