- Keep it simple
- Use Meaningful Symbolism
- Use Two to Three Basic Colours
- No Lettering or Seals
- Be Distinctive or Be Related
The other rules for flags are less of a problem for football helmets. Almost all of them depict the team mascot in some form or other (meaningful symbolism), and teams almost universally have two main colours. I complained about excessive lettering on some helmets, but I am more lenient about the idea that one to three letters (which serve as initials) make sense on a helmet more than on a flag.