This is a fairly simple answer. The bill is a simplified rendition of the John Trumbull painting Declaration of Independence. "Trumbull also painted more elegant furniture, covered the windows with heavy draperies rather than venetian blinds, and decorated the room’s rear wall with captured British military flags, believing that such trophies were probably displayed there." https://www.aoc.gov/explore-capitol-campus/art/declaration-independence You only see the smallest part of the captured flags on the 2$ bill.