DLC or anything to do after the story?

[Jostabeere]

So I finished the story and all side missions. Is there anything left to do besides collecting the, well, collectibles?
I still have a main quest marker on the bridge, yet nothing happens.
And what about the files within the games folder that are marked as DLC? Is it just the soundtrack?

[B Dawg]

Multiplayer. The DLCs were just outfits, weapons and multiplayer maps.
If the quest marker is on the bridge, it means you completed the game.

[Spicy Lobster]

If I remember the soundtrack (OST and Licensed music) are separated in multiple files, all of them encrypted in fsb files in a folder and requiring a password to open them :)