According to a new trailer hosted by Eurogamer, the DLC will contain 35 new maps, 50 new objects for the level editor and 5 new tournaments. The DLC will also pack three more Achievements, which should please all the trick jumping masters out there. Head over to Eurogamer for the trailer, and keep an eye out for the Big Pack, which hits XBLA on December 24 for 800 points ($10). (via joystiq)
The Trials HD Big Pack DLC will hit XBLM on December 24th. The new DLC pack will include 35 new maps, 5 new tournaments and 50 new objects for use in the level editor, also the pack will also include 3 new achievements to go after also. If you need some more Trials HD action this content can all be yours for 400 points ($5).
EDIT: Via Major Nelson its seems the week of the 23rd you can pick this up for only 400 points ($5) as part of the Holiday deal program and not 800 that Joystiq posted.