here's the steps to do it:
/dopackicons
wait a few seconds
then do /doicon (brick uiname here)
it will take a screenshot and save it in IconShots/(the uiname you entered).(the screenshot extension type)
thanks, locked
EDIT: doesn't appear to work
/dopackicons works, but then I enter /doicon stairs; nothing happens, and there is no IconShots folder
EDIT2: cycles through the players backpack items, the command TomTom told me about doesn't do this