We know that DC movies not include post-credit scene but in 2011's Green Lantern we had one of them.
What happened at Last
Superman and Batman are done fighting each other and are united against a common threat (may be Lex Luthor is his battle amour or the Doomsday) with the help of Wonder Woman.
The scene directs to the Batcave were the heroes had strated off the formation of The Justice League.
We see Lex Luthor escorted by the guards of Metropolis Central Jail. He is then uncuffed, the doors get locked. He sit at the side of his bed.
Then a deep, dark voice is heard from the shadows stating :
"Now we wait, my associate will carry out my work."
We see Clark Kent/Kal-El sleeping with on his bed with Lois Lane. The camera focuses on Kal's forehead. He will dreaming about Kara-Zor El, that how she landed on the Earth is of the scout ship. (He would had just some glimpses of her).
Then Clark wokes up and says "Kara".
Note: The glipses would be from Man of Steel Prequel comic. Which was an official tie-in comic in DC Cinematic Universe.
I hope you enjoyed this article. Batman vs Superman : Dawn of Justice will be realising on 25th July 2016.