Tardis 18:
Winner: Restiveness
Prize: 64 diamond blocks (provided by CovertRaw, wblaine128, and myself)
Note: took over 3 hours to find
Picture:

Tardis 20 (a few days late):
Winner: ????
Prize: none yet (stilll don't know the winner)
Picture:

@cepheid Tardis 20 (a few days late):
Winner: ????
Prize: none yet (stilll don't know the winner)
Picture:

restiveness won