Full list of all 15 ilomilo achievements worth 250 gamerscore. It takes around 8-10 hours to unlock all of the achievements in the base game on Xbox 360.
The base game contains 12 achievements worth 200 Gamerscore, and there is 1 DLC pack containing 3 achievements worth 50 Gamerscore.
Helped find all 10 floating eggs with the fly while playing cooperatively
Completed all bonus levels
Completed the game
Advanced to chapter 4
Defeated a Nabber in the same move as you completed a level
Advanced to chapter 3
Got a score of 500 points or more in the ilomilo shuffle minigame
Played the solo instrument to the music theme in the main menu
Advanced to chapter 2
Collected one safka of each color
Completed the tutorial
Completed a level
Pointed on all the 5 floating eggs with the fly while playing cooperatively (autumn tale)
Completed all bonus levels (autumn tale)
Completed autumn tale (autumn tale)