Look at pictures of real hot air balloons.
As mentioned: sand bags and land lines trailing. Lines connecting the basket to the balloon.
But also:
the burner
lines across the balloon to show the structural lines (they appear to go across the balloon)
The largest one you might consider a silhouette of a person waving.
Or silhouette of a person on the ground waving to the balloons.
When I quilt it, I would do lots of wind blowing across the quilt.