Artwork Fragment Chests (I-VI) fill the Art Hall Exhibition Halls; Chests V and VI (for Knight Equipment and Mask halls) are hardest. Best free strategy: smash lots of Crazy Eggs and farm Lv1 Junior Hydra to collect Magic Artwork Chests (each gives a random Artwork Fragment Chest I-VI). Free sources per tier: Chest I from Lv4-6 tiles (lucky), normal monsters Lv11-21, Black Market 5/1,000 gems. Chest II from Lv7-10 tiles, monsters Lv19-30, Black Market 5/1,500. Chest III from Lv11-12 tiles, monsters Lv31-35, normal bosses Lv1-6, Garuda + Viking Icebreaker, Black Market 5/2,000. Chest IV from Lv13-15 tiles, bosses Lv7-8, Royal Thief, Viking Berserker, Black Market 5/2,500. Chest V from monsters Lv24-40, bosses Lv9-17, Lava Turtle/Golem/Witch/Warlord/Ymir Lv1-5, Hydra Lv1-4, Viking Chief, Nian, Royal Thief, Black Market 5/3,000. Chest VI from Royal Thief Lv1, Black Market 5/3,500. Magic Artwork Chest (best free source): 100% drop from Lv1 Junior Hydra (contains 3 chests; NOT Medium/Senior Hydra); Crazy Eggs give 40+/day. For a bot, farm Lv1 Junior Hydra and Crazy Eggs to fill the Art Hall (which then pays gems, stamina, speedups and teleporters).
Original research source: Evony Guide Wiki