Here are some ideas to make bonus objects more interesting:
poisonous objects that decreases score/ increase caterpillar length
object that is constantly MOVING (but at a slower speed than the caterpillar)
ALL objects FLASH before they disappear?
High score objects put at the CORNERS (hardest place) when the game speed is very fast?
"Gates" that the caterpillar can pass through to gain points, but the "fence posts" of the gates are obstacles - you die when you bump into them.
^could lengthen the "gates" to form mini mazes that are 3-5 squares in length.
An object that is always one square behind the tail of the caterpillar (so it moves with the caterpillar)
Here are some ideas to make bonus objects more interesting: