Long before the new X-Men: First Class trailer was turning heads, Paolo Rivera painted Charles Xavier and his young, original lineup of mutants for Mythos: X-Men with Paul Jenkins. He did the same for Ghost Rider, and as you can see in his online journal, he's caked a few colors onto a host of hero portraits in various studies and sketches.

Rivera's Self-Absorbing Man blog boasts appearances by Marvel's most famous big-screen Avengers of the last few years, including Iron Man, Thor and Captain America. Unless you've been watching his posts regularly, you may also have missed an epic Hellboy piece he shared a few months ago.
Rivera really nails the old-school Jack Kirby shapes and physiques of Doctor Doom and Annihilus, and his final products look about like what you might expect to see if Alex Ross painted over some old Kirby test drawings. Gaze upon them below, and prepare to feel sketchbook envy.