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