Here is the full list of all 26 PictoQuest achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Beat Moonface
Finish all quests
Beat the mountain boss
Beat the mangrove boss
Buy all life extensions
Reach 5000 gold
Beat the seaside boss
Beat the desert boss
Beat the cave boss
Loose 10 times
Use the thunder orb
Beat the swamp boss
Beat the forest boss
Use the ice orb
Beat the plains boss
Use the fire orb
Use a potion
Have a full inventory
Beat the village boss
Finish a three-monster grid
Read the tutorial
Reach 0 gold
Make 20 mistakes
Finish a two-monster grid
Finish a one-monster grid
Finish the first grid