Here is the full list of all 12 Gnomes Garden 3: The Thief of Castles trophies - there are 7 bronze, 4 silver and 1 gold.
For restoring the signal fires
For stopping time
For restoring Stonehenge
For growing a lily pad
For activating an altar
For speeding up construction
For getting rid of a Gremlin
For speeding up workers
For restoring a plant
For constructing a building
For defeating the evil warlock
For completing all levels with 3 stars