Best case scenario, you manage to get to the right person who is willing to allow you to put a picture of the kilt on their web site. See what happens. If it doesn't take off you are out only a small cost.

I would imagine though, they are going to want to reasearch your ability to provide a kilt to everyone who orders one in a timely manner since the customr is buying from them and not you.

I think you would be within your rights to make kilts which happen to match the team colors and sell them on a web site maybe named something like "www.northamericanfootball kilts.com". Then you could purchase NFL & AFL patches and pins from an authorized dealer to sell in conjunction with the kilts and maybe sell a "application service". Then you are not tying yourself to the football leagues.

Disclaimer: I'm no lawyer and this post is no way represents anything but an opinion and we no what those are worth