I have no idea about portraits, but I like Wayne Reynolds work a lot.
I saw his upcoming cover for Green Ronin's The Black Company at Gen Con and thought it was amazing. Folks told me that the piece had been roundly derided on the GR boards, and I thought "well what were the nimrods hoping for exactly"?
Reynolds is also responsible for pg 16 of WotC's Sword and Fist...possibly the only thing I like about the supplement