I made this card for the 3D contest for SU demonstrators last month. It didn't win so I'm posting it here. I got the idea for the diorama scene from a VSN challenge (MAR07VSNH) to make a room/scene.
The scene is made on a square, scored in the middle in both directions, then cut to the centre line on one of the folds. I added an extra diagonal score to allow this to fold flat to fit in an envelope. The dinosaurs are popped up in traditional fashion.
The foreground needed a bit of something so I made a pond with greenery (the treetop stamp).