Probably best to do it so that you put your own avatar on the front of your own T shirt/sweatshirt and you can send off for an 'iron-on' NOOL transfer/design that you can then just apply to the back of the shirt. That way, everyone has their own design, but with an 'official' NOOL stamp on it too.
It would be easier and cheaper for creating the things, post and packing, etc.
PLUS, as Al said, then we don't look like 20 identical tits if we all turn up at a gig or pub and meet up. We just look like 20 individual tits, wearing nonsensical avatars on out chests... 
