Having recently read Bram Stoker's Dracula I was impressed by some of the images created by his great descriptions of scenes. One in particular was of Dracula descending his castle wall, 'Once more I have seen the Count go out in his lizard fashion.' So I was inspired to sketch the scene. Creepy.
I 've also been listening to the HP Podcasts having read a bit of Lovecraft lately and they mentioned I.N. Hubbard's illustrated version of 'At the Mountains of Madness.' It could never be as engaging as the original text, but a worthy attempt to bring it to life.
If you are a dabbler in cartooning or scribbling then classic literature serves as a great inspiration. Give it a go and sharpen your skills.