As great as the new series has been, I can't help but still think of The Doctor as the old man William Hartnell. I think it might be from going back and watching a bunch of those original episodes to see where everything all came from in the first place.

I can't remember Tennent well enough to compare just how close your sketch is to him, but it's not too bad. Not used to black and white pencil sketches I take it though?