I host a monthly theme swap over on Docrafts for ATCs - this months theme was Reindeer and here's a few I have made ready to go out at the end of this month.
If you would like to join in 2015, there are very few rules - you can use any style or techniques, the cards must measure 2.5 x 3.5 inches and up to 4 can be swapped every month
January's theme is Cars and further details can be found on the Docrafts ATC forum