Given the enormous cost and the high energy content of the thing (all that cement, steel and chugging round in big chuggy things), how long will it be until we get back as much tidal energy as the fossil energy we put in? Will the sea level have risen so much by then that the thing stops working?

The photographer owns copyright on their image, unless they have passed it on to somebody else. There are companies who buy up images and sell licenses for a living.

Sometimes the location, such as a museum, will own the artefact being photographed and their permission may also be needed.

AFAIK nobody can stop you publishing a photo of something that has been on public view and legally snapped by a passing photographer. But if the photo was taken behind closed doors, the design owner may have control too.

Somewhere like the Wikimedia Commons has supposedly freely-available images. But it is wise to check the small print of the license, and also to take a view on whether the image might have been uploaded illegally by a rip-off artist. For example some licenses do not allow commercial use, as in a company logo. You would not be able to register the logo as belonging to your company unless the image owner/s had specifically released it under a suitable license.

Similar issues can arise over the use of a registered trademark such as the word “Spitfire”: you might get away with calling your company say Super-Fighters Ltd. but not Super-Spitfires Ltd, and you might not be allowed to say that the image in the logo was a Spitfire.

If you just drew your own image (but not traced another) or took your own photograph of a machine in a public place (e.g. not a privately-owned airfield), photoshopped out any proprietary markings such as registration IDs or RAF roundels, never said what it was and steered clear of any business activity which might be seen as competing with the license owner, you should be OK. Otherwise, you’d need to check the licensing.