David,
Oooo that would be great!
Building something out of something else is STRICTLY forbidden and entirely against the spirit of the competition.
Punishments for infracting this rule plunge new depths of ghastliness.
It has to be the original object with embelishments (in order to win!) OR:
1) Some animal made out of objects (a cow made out of beer cans would be acceptable)
2) A house-type PB made out of other stuff
or
3) A something else made out of post boxes.
This is what we get up to in Summer. You should see how daft it gets when winter sets in!