As far as I'm concerned, John Howe is king. My favorite painting, LotR related or not, is his one of Smaug. It's breathtaking. Click
here for the site of his work and see what I mean. I just greatly admire his ability to capture a piece of the action in a painting and have it be so real, like he took a snapshot with a camera during the battle.
The other artists mentioned earlier are wonderful, too. I have a calender by Ted Nasmith. It's wonderful. This month is his Oliphaunt. [img]smilies/biggrin.gif[/img]