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