More fun with Post-it Notes

Recently, this was spotted in the window of an office complex near our apartment:

Apparently, someone else has a surplus of Post-it notes and even more time on their hands than Mr. Have a Nice Day (see two posts previous). I'd say something disparaging right here if it wasn't such nice work.
Next time, office artiste, I would like to see a Hoth action scene. How many Post-its in an AT-AT?