I think the cards that recently got facelifts would have made very good foil cards myself.
Chimera is a cool and fun card, but it only sees limited use in decks. The cards that just got new art (vampire, chrysaora, shrieker) see much more use.
I think cards that are very commonly used would make ideal candidates for foils.
(Personally, I'ld love a foiled Pharaoh myself. Its my favorite card and I use it frequently)