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 the desert boss
Loose 10 times
Reach 0 gold
Buy all life extensions
Beat the cave boss
Reach 5000 gold
Use the thunder orb
Beat the swamp boss
Make 20 mistakes
Beat the forest boss
Use the ice orb
Beat the plains boss
Use the fire orb
Use a potion
Read the tutorial
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
Beat Moonface
Beat the seaside boss
Beat the mangrove boss
Beat the mountain boss
Finish all quests