Those kallistra ones look nice, very similar to the Pendraken medieval wagons - although the stowage in the second wagon is only kallistra
In the Pendraken ECW range there are Tumbrel wagons, which are 3 sided wicker wagons, more square based than the kallistra ones. They also have barrels in the Artillery Accessories pack - this is a very handy pack
In the Pendrakan German WWII range, there is a 4 wheeled covered wagon, that is quite generic. There are also a pack of boxes and sacks - the boxes are probably a bit modern and the sacks aren't too exciting.
As you say the dungeon accessories range has all sorts of useful bits, the crates and treasure piles are particularly useful.
This is the treasure pile and table and chairs to make a paymaster for my dogs of war
Selection of Pendraken Wagons
ECW tumbrels on left, SYW in middle, Medieval to the right, and WWII at far right
