John Hall writes:

In message 20160902184241.0f75172e@amaterasu, Mike Causer
writes
Does any have or know of an archive of decent quality pictures that
we could use. I'm afraid there's no money in it and probably no
credit either, they never credited the ones I've given them in the
past 10 years -- unless I do the artwork and sneak my name in
somewhere discretely.

If they were prepared to wait a few weeks I could take enough photos
myself but this needs to be printed for an event in early October,
so we cannot wait. Can anyone help please?

You could try Wikipedia. Any photos they have of cloud types as part
of their articles will be in the public domain.

Most images on Wikipedia will have a license that is more or less
permissive, but it will very often insist on attribution at the very
least. (I checked half a dozen at random and they all did.)

--
Ben.