Although I agree with LadyBattousai - that the characters are the embodiment of their emotions and action - I appreciate when an author describes their characters. Of course I impose my ownopinions of what they look like, based on THEIR interpretation. The cover illustrations, are granted, sometimes rather irritating, but in the end they dont impart anything on my own image of the authors description of the characters.
I watched a program on cover models for books. (It had that Fabio guy in it.) Anyways, the authors dont always have a say in who the model for the art is.
As a reader of fanfiction, I ALWAYS like to see the artists vision in artwork (either their own, or commisioned) If the images don't mesh with my own, its not a turn off to the story or anything. Likewise, its nice to see what other readers "see" when they post art to another persons story.
I'd draw your pictures, if I were you!