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
Buy all life extensions
Reach 5000 gold
Beat the mangrove boss
Beat the seaside boss
Beat the desert boss
Beat the cave boss
Use the thunder orb
Loose 10 times
Beat the swamp boss
Use the ice orb
Use the fire orb
Beat the forest boss
Beat the plains boss
Use a potion
Make 20 mistakes
Reach 0 gold
Beat the village boss
Have a full inventory
Finish a three-monster grid
Finish a two-monster grid
Read the tutorial
Finish a one-monster grid
Finish the first grid