Here is the full list of all 49 Create achievements worth 1,000 gamerscore. It takes around 30-35 hours to unlock all of the achievements on Xbox 360.
Collected all 610 Sparks
Used every brush in Paint mode
Placed all types of animals throughout the game
Eaten 50 slices of toast
Used every type of rocket within challenges
Saved a Creation or a Challenge from Free Create
Placed the Create team's favorite animal!
Finished five Create Chains on a level
Solved a Contraption-o-Matic Challenge with a contraption built of 40 or more parts
Solved Challenge 10 in Transportopia entirely with Horseshoe Magnets
Collected 501 Sparks
Unlocked Future World II
Unlocked Outer Space II
Unlocked Family Home II
Unlocked Theme Park II
Collected 284 Sparks
Attached 50 objects which have string to Challenge objects
Unlocked Darkworld
Unlocked Pirate
Unlocked Urban Sports
100 balloons burst
Unlocked Future World
Unlocked Ancient History
Completed a car based challenge after all its wheels had been burst
50 explosions set off
Unlocked The Great Outdoors
Collected 100 Sparks
Unlocked Outer Space
Driven 2,000 meters in vehicles within Challenges
Reached a x20 multiplier in a Scoretacular Challenge
Unlocked Family Home
Unlocked Transportopia
Uploaded a Solution
Submitted an entry to a Community Challenge
Solved 20 player generated Challenges
Solved 10 player generated Challenges
Solved a player generated Challenge
Marked the content of 10 different online users as a favorite
Uploaded a remixed Creation
Uploaded a Creation
Remixed and saved a downloaded Creation
Downloaded an EA Pick
Downloaded another user's Creation
Marked an EA Pick as one of your favorites
Marked another user's content as one of your favorites
Rated the Creation of another online user
Unlocked Theme Park
Solved your first Challenge
Earned your first Spark