Scooper ‘5p1d3r’ tells us that Thomas Haden Church talked briefly about the Spider-Man 3 villains:
I was listening to the Opie and Anthony Show (nationally syndicated) this morning and they had Thomas Hayden Church on the show. At the very end a caller asked how it was to play Sandman and what Venom would look like. After threatening an anvil on the caller’s head for divulging information, he did briefly mentioned that he has been having a good time and had been filming for months. “A lot of sand and a lot of man.”
*minor spoiler* He did say that Venom would look a lot like the comic book Venom and then they moved on.