> It is the cover illustration that I vaguely
> remember and that has haunted me all these years;
> there was one, or more, sinister evil-looking
> priests or monks, robed, standing in a field of
> opium poppies. I doubt that it was a C. A. Smith
> collection, but it may have been a collection of
> different classic horror authors.
This must be it:
[
www.aumania.it]
It's by Bruce Pennington (responsible for some excellent Smith covers too) and is used on at least the second volume of the Panther Books edition of
Tales of the Cthulhu Mythos by H.P. Lovecraft and others, edited August Derleth.