Having gone through the other replies i would like to suggest the following., some have already been mentioned. Mostly US stuff
Spare hvss road wheels
Individual 30 and 50 cal ammo cans as opposed to a bunch, some could be have open lids with ammo exposed
Few lengths of above ammo.
Spare tools such as sledge hammer,axe,shovels etc
US pioneers tool rack both empty and full of tools.
Some tank ammo 75,76,105 loose rounds maybe an open box with rounds.
Wood tank round boxes.
Ration boxes
Radio sets
As mentioned air cooled 50 cal.
And any equivalent British stuff such as radio set , open ammo boxes with round lewis ammo mags, 17 pdr ammo etc