Yes, for the two books that I have out or are just about out, when we did the cover reveal I asked my editor if it was OK for me to reach out to the illustrator and give them a heads up that we were doing a cover reveal as it feels weird, to me, as an author, to get all the "congrats" and such when the cover has hardly anything to do with me! And each time the editor said yes.
So I DMd them on Twitter, thanked them profusely for their beautiful work and let them know that we were doing a cover reveal and I hoped they were OK for me tagging them on it. My illustrator for FREAKY, FUNKY FISH and I communicate occasionally through DM and she is illustrating the next book in the series due out next fall. I've never had more conversations with my illustrator for TELL SOMEONE though I certainly tag him in anything about that book.