Everyone does blank sketch covers, comic books published with a vast white expanse on the cover with the aim to be given to artists to create their own unique sketch covers for the comic in question.

Sketch covers — comic books sold with blank covers or at least big, blank spaces on the covers where fans can get original art drawn on them — are some of the most popular variant covers in the comics ...

Co-creator of The Boys, Darick Robertson, posted about a sketch he had done at a comic book convention of Butcher's dog, Terror, with Spawn's mask in his mouth. I am happy to see this has never sold.