I first saw this custom done over at Larsworld. I think he does cool stuff with action figures. The base figure is an Aquaman from the JLA Classified series and parts from John Stewart Green Lantern, Martian Manhunter, and ML Series 1 Captain America.
When Lars did his, he smoothed out Aquaman's chainmail using resin. I'm not much of a sculpter and was afraid of what I might do, so I instead cut Aquaman's arms and torso off and replaced them with Green Lantern's. The boot cuffs are from Martian Manhunter, jus trimmed down some, the belt and gloves were made from Apoxie Sculpt, and the shield and wings came from a Series 1 Cap. I think the red looks funny in the pictures, I'm not sure if it was from the camera or PS, it looks a litter darker in person.
I'm pleased with the way he came out and I'm tempted to make more Avengers in the Ed McG style, probably Hawkeye next.