Little baby icons over each parcel or something.
Maybe just show the item on the cart as a smaller version of its in-game sprite?
I don't know what the answer here is, all I know is that having to pick up 6 items to figure out where my water barrel is while I'm mining is annoying. (or trying to remember where I put the water barrel in the cart)
I just don't think "generic sack sprite" is the right answer.