For home games, as said before the half of West stand lower could be used to house these flags. Maybe the club could invite any fans with any flags from around the world with something Barnsley orientated emblazened on them to hand them in to the club so they could get groundstaff to set them up. Would look great. Could only put the club in a good light to show our solidarity for players from whatever country they are from. Be nice to see some more variety away from home too.
