Walt's take on the Riddler has the 60's Batman vibe. I think that series captured the Riddler most accurately of all the series villains. His green and purple design is classic and parroted by other comic book classics such as the Green Goblin and the Incredible Hulk. I like to have some orange in the suit since I grew up watching Jim Carrey riddle it up in Batman Forever. I think one of the most believable and cool designs for the Riddler was from The Batman cartoon that in the 2000's. He looks like Marilyn Manson and is a bomber who has riddles in his bombs that can diffuse them. The next time the Riddler makes it to the big screen I wouldn't be surprised to see him interpreted like that.
Clayface has become an archetypal comic book baddie for both aspects of his character. One he's a shape shifter paving the way for the likes of Mystique, the Skrulls, Primus, and Inque. The other villain archetype Clayface cements is the amorphous blob villain which has spawned such imitators as Chemo, Plasmus, and Spore(from the Astounding Wolf-man/Invincible Universe).
There have been eight Clayfaces in the comics. The traditional and iconic Clayface that comes to mind when people mention him to me is the amalgam Clayface used in the BTAS. That Clayface was a has been actor named Matt Hagen who is disfigured and needs Daggets special face cream to keep his good looks. Things go awry and he's mutated into the big amorphous clay monster. This amazing animation and the voice performance by Ron Perlman is classic, and makes Clayface one of my top 5 Bat villains. It looks like a piece out of an Oscar worthy anime.