For our Rotterheim campaign we did not do the usual start with building our warbands but instead we are now in the process of writting the background first! Our campaign will not have the usual twintailled comet but more of a plague/zombie infested start. Much like medieval walkin dead. The goal is to play our usual games of mordheim and every 5 or so games play a massive fluff game with NPC's and more! If you like to follow the campaign you can read parts of it on my blog:

http://shamanpainter.wordpress.com