There is home movie footage shot of the cast and crew drinking in Plockton but it has been removed from YouTube due to the owner's concerns. You can see it however in this Internet Archive link.

There is some additional footage, from the same owner, that is up on YouTube, It starts with Howie shouting at the girls in the window with their masks on. It also includes scenes of Howie and others in the cast drinking with the locals many of whom you'll recognize as being in the movie. You can see that here. There is more footage of both scenes but until that comes forth, this is the only footage that shows the film being made that is available right now. (A blooper reel exists. It was shown in Falkirk in 1998 as well as London in 2000.) See more on all this here.

AP archive footage (brief - from :44 tp :47) of the Wicker Man at Cannes, 5/11/73!

Still pictures

See the above link for specific scenes.

Other pictures/scans:

Editor's script