I'm not certain but I think they're basically extras. I always assumed they were fans and that the picture was candid, especially when I was younger and didn't know any better. But of course now I realise the covers were staged.
The girl in the Salvation Army bonnet (a prop) was Australian and happened to be living in Sweden at the time. The car had belonged to Torsten Kreuger, brother of Ivar, a major international crook of the early 20th century.