The Frankenstein cover painting is gorgeous. afraid i've not been able to find anything else of Huens's in the horror genre, though with a bit of luck one of the others will set us straight. He seems to have been far more prolific illustrating fantasy and fairy tales.
From the first, I set myself against "literature"; the story was the thing, and no amount of style could persuade me to select a story that lacked genuine, unadulterated horror. For those who wanted something high-brow there was plenty.
The only other horror fiction cover that I know is for 'Dr Jekyll and Mr Hyde and other macabre stories' published alongside the Frankenstein edition by Corgi books. The cover showing Mr Hyde is every bit as good as the Frankenstein.