RIP John Paul Leon. His art first made its impact on me back in 1996 when he did The Further Adventures of Cyclops and Phoenix and his redesign of Apocalypse blew away my 14 year old mind.
When he did Earth X in 1999 his design work in that series just really captivated me and I always appreciated his version of X-51.
Do yourself a favor and go pick up some of his works, you won't regret it.