Follower of the Way
It's absolutely William O'Connor. And that piece definitely is eye-catching. I can't find my original piece that made me want to play Avenger. It was a darker-toned piece with a greataxe-toting Avenger--IIRC, a half-orc, but I could be mistaken.I think that's a William O'Connor piece.
I didn't strictly need an image to make me fall in love with Dragonborn or Paladin, but this image is burned into my memory as what a proper Dragonborn Paladin should look like.
Here's Ben Wootten's DA upload of it, to give credit where credit is due.
I also swear I remember an image of a dark-robed half-orc Avenger with a greataxe, which was absolutely the image that cemented the Avenger archetype in my mind. But I have no idea where I saw it or who made it, so it's...pretty much lost to time now.