During the Credits
There are no extras during the credits, besides the ability to change the speed of the credits.
After the Credits (spoilers)
There is a message after the credits that says:
WINGS OF LIBERTY COMPLETED!
The Zerg invasion has been stopped, and the Queen of Blades has been restored to her original form of Sarah Karrigan. But the victory has come at a heavy cost; Tychus Findlay is dead, and Arcturus Mengsk remains secure on his throne.
Discover Kerrigan’s fate and the fate of the zerg in Heart of the Swarm, the next chapter in the StarCraft II trilogy.
There’s also the option to continue playing the campaign by going back and replaying missions that might have been skipped before starting the final mission.
Songs During the Credits
LVL80ETC – Terran Up The Night