A cute way to make an unusual advent calendar is to make tiny envelopes and attach these to a piece of card.
Use rubber stamps to decorate the paper and add the numbers to the front of each envelope. Write a motto or sentiment on a piece of paper and pop this into the envelopes so that one will be opened each day - or if you fancy something a little more interesting how about popping a forfeit or challenge into the envelopes...? There are lots of ways this idea can be developed. Have fun!