Lovely. One of those images that actually hits me smack in the face and leaves a mark.
Loving the manipulation of the colours, adding all the more to the sense of imprisonment, confinement, and offering a glorious contrast to the bright, joyous world beyond.
I really like all those little handles. Their completely random angles offer asymmetry, something delicious for the eye. They even have character, and almost look like people. They seem to be beckoning, or perhaps taunting, depending on how one likes to look at this.
All in all a very interesting take on a very widely-understood emotion and concept.