Hey box1, the Sturm is a great kit, whether it is Tamiya or Italeri. There are quite a few aftermarket detail sets out there. Here are a few things you can get to make that Sturm really sexy
Verlinden Fenders and Zim (although I do not recommend photoetched zim)
http://www.verlinden-productions.com/vp_htm_1201_1600/vp1462.htm
Aber photetched Set (the best IMO):
AB35043 Sturmtiger details
Aber fenders for Sturmtiger:
AB35A43 Sturmtiger Fenders
Eduard Photoetched set
ED35085 Sturmtiger
I know that Tamiya sells aluminum 38cm Assault Mortars for the STurmtiger but can not find the item number.
Hope this helps box1, the Sturmtiger is a great kit.
Cheers
Rob