Personally, I'd suggest using Chaos against Empire; both humanoid minis but definitely good vs. evil. (With all the great minis in both lines you'd be spoiled for choice as well.)
Sigmar Priests for Bishops, and Engineers for Rooks. Can't think of good king or queen minis. Pawns could come out of the generic box, or one of the pikemen/spearmen from the dogs of war line.
Lizardmen would be a great opportunity to use an array of colors, you might need a warmaster magepriest as king just so he'll fit on the table. But the temple guards as rooks, cold ones as knights, and Skink shamans as bishops, with skinks for pawns could look great. You could oppose them with Tomb Kings, jungle vs. desert style.
Otherwise, I suggest Dwarves vs. Goblins (the featured armies in the latest edition of WHFB, or (Wood) Elves vs. Dark Elves.
Very pricy, but funny would be Ogres, with Gnoblar pawns, vs. Skaven, a verybig vs very litlle look on the table.
I guess you are spoiled for choice already, I'd hate to have to decide, I'd probably go for something like Good versus Evil just so I could do a bit of everything.