there are several tourney server ingame, just join and play and with a bit skill and luck u may win some little prices.
the other thing are events, which are hosted by the GM´s or some people which just thought "lets start a event".. these are mostly replay based, so they give u a certain mod and say "make blablba" and the one which makes "blablba" the best, wins.
http://forum.toribash.com/forumdisplay.php?f=37
this is the event board, just take a look up into it.
also once in the year is a world cup, where everyone can participate. and the winner gets some good prices!