This concept taps into an already existing wealth of theme variability including sports and teams, cartoon and movie characters, rock bands, patriot, novelty, holiday and seasonal, etc. It's a wonderful blend of flag, banner, windsock, and kite flying. Two different frame systems fit the most common size flags and banners on the market, with hundreds of possibilities to choose from. Nearly any flag or banner can become a kite in an instant. Lightweight polyester flags and banners work best and are the least expensive.
Nylon is also good, although heavier and usually more expensive.
Cloth fabric can be cut to size and hemmed to make your own sail. This makes it easy and fun to make custom kites. The cost of complete kites, ready to fly, depends on the components chosen. Flagkites need no tails to fly, but can be added for adornment and a little more stability if desired. Bannerkites need two tails to fly.