Here is the full list of all 30 Pepper's Puzzles achievements.
You completed everything! Congratulations!
Complete all classic puzzles with 3 stars
Complete the Classic category "Run out of Ideas"
Complete the Classic category "Extinct Animals"
Upload your first puzzle to the Workshop
Complete the Classic category "Apocalypse"
Complete the Mosaic puzzle "The Apprentice"
Complete the Classic category "Space"
Complete the Classic category "Movies"
Complete the Classic category "People"
Complete the Classic category "Daily Routine"
Complete the Mosaic puzzle "Moonlight Warrior"
Complete half the cells of a Mosaic puzzle
Complete the Classic category "Sci-Fi"
Complete the Classic category "Art"
Complete the Classic category "Animals"
Complete your first cell in a Mosaic puzzle
Complete the Classic category "Food"
Complete the Classic category "Fantasy"
Complete the Classic category "Life in the Farm"
Complete the Classic category "Warm up #2"
Complete the trial "Marathon" with 3 stars
Complete the trial "Meek VS Giant" with 3 stars
Complete the trial "Climb" with 3 stars
Complete the trial "10x10" with 3 stars
Complete the trial "7x7" with 3 stars
Complete the trial "5x5" with 3 stars
Complete the Classic category "Videogames"
Complete the Classic category "Warm up"
Complete a classic puzzle with 3 stars