Here is the full list of all 12 Medieval Defenders trophies - there are 7 bronze, 4 silver and 1 gold.
Build 50 towers
Kill 1,000 enemies
Manually send 100 waves of enemies
Sell 30 towers
Earn 100,000 coins
Kill 500 enemies with spells
Complete level when your castle has 1 HP
Build 1,000 towers
Kill 50,000 enemies
Fully upgrade 200 towers
Sell 500 towers
Complete all levels with 3 stars