DLC

There were three challenge packs released, two character packs and console themes.

All the Trappings Challenge Pack 1
RELEASE: 7 January 2011 (Steam) | 19 December 2018 (Xbox Marketplace)
DEVELOPER: Crystal Dynamics
PUBLISHER: Eidos Interactive
PRICE: $2.99 | £1.99
STORE DESCRIPTION: Four new challenge maps filled with hordes of undead enemies and devious traps you must maneuver and exploit to survive.

Things that Go Boom Challenge Pack 2
RELEASE: 7 January 2011 (Steam) | 19 December 2018 (Xbox Marketplace)
DEVELOPER: Crystal Dynamics
PUBLISHER: Eidos Interactive​
PRICE: $2.99 | £1.99
STORE DESCRIPTION: Four new explosive challenge maps featuring a variety of tense puzzles, deadly traps, and relentless combat encounters.​

A Hazardous Reunion Challenge Pack 3
RELEASE: 8 December 2010 (Xbox Marketplace) | 7 January 2011 (Steam)
DEVELOPER: Crystal Dynamics
PUBLISHER: Eidos Interactive​
PRICE: $2.99 | £1.99​
STORE DESCRIPTION: Four new challenge maps featuring mind-boggling puzzles, waves of intense combat action, and a fiery reunion with an old friend.​

Character Packs

These character packs don't change much in terms of gameplay but cutscenes are different.
Kane and Lynch Character Pack
  • Store Description: Grab a friend or go at it alone as gaming’s most notorious criminals find themselves in Lara Croft’s world and must work together to fight their way out.
  • Released: 22 December 2010 | 7th January 2011 (Steam)​
  • Price: Free

Raziel and Kain Character Pack​
  • Store Description: ​Grab a friend or go at it alone as Kain and Raziel from the Legacy of Kain games. The two iconic characters must work together to defeat a new threat in an unfamiliar world.
  • Released: 15 December 2010 (Xbox Marketplace) | 7th January 2011 (Steam)
  • Price: $2.99 | £1.99

Source:

Images are from Steam and the Square Enix North America Store