Here is the full list of all 12 Psychonauts in The Rhombus of Ruin trophies - there are 9 bronze, 2 silver and 1 gold.
Escape the Rhombus
Save Loboto
Rescue Coach
Rescue Sasha
Rescue Lili
Rescue Milla
Locate the Rhombus of Ruin
Help Coach out... with fire
Play the song melody on the keyboard in the Cruise Ship
Create the spiked leather jacket on the UFO
Listen to all of the radio stations on the Bus
Solve the sliding box puzzle on the Train in 20 moves or less