Rittenhouse Archives is releasing Marvel: Greatest Heroes in March and will contain 1 full color Avengers based Sketch card in each and every box. And, if You haven't seen it by now, Rittenhouse is featuring the Sketchcard samples of said card set by running a very cool Sketch Card Artist Of the Day on it's Facebook page. I would highly recommend taking a visit to see some very impressive artwork. They are featuring 1 or 2 artists 9-card samples every day from now until the set is released. From what I've seen, It's looking to be one of the best looking sets yet.
... and yes, this is the set I'm doing a few Sketches for. More on that / those later.