There are some really interesting examples of illustrations of Sir Arthur Conan Doyle's Sherlock Holmes. The first person to illustrate the character/stories was the artist Sidney Padget. I've heard various stories, such as at first Conan Doyle expected a different (less pretty) archetype for the character, and then decided that the Padget interpretation was fine. They also apparently mistook Sidney Padget for his brother, who was actually more famous at the time.
After Padget's illustrations, not many different stylistic archetypes have changed about the character, and you can definitely see his illustrations in the aesthetics many film adaptations of the stories. It's hard to say how much is due to the direction of the author's descriptions vs. the artist's interpretations though.
the first print illustrations of the story (I couln't find the artist information in the book I was looking at)
below are two Sidney Padget illustrations (along with some actors, etc.)
I found Wyndham Robinson's illustrations very interesting. He was mainly a cartoonist.
these are all from "A Sherlock Holmes Scrapbook".
you can find more of sidney padget's illustrations here: http://www.arthes.com/holmes/
and a whole bunch more: http://commons.wikimedia.org/wiki/Category:Illustrations_from_books_of_Sherlock_Holmes
and more about wyndham robinson here: http://www.cartage.org.lb/en/themes/arts/drawings/Cartoonography/SatiricalArt/case2/case2.htm