For art commemorating the events of 9/11 or other tragedies that didn't happen the 1990s, the rules are different.
Pictures honoring these events are allowed, even if they contain characters that aren't from the 90s or before, as long as the tragedy in question is properly respected in the pic, and not insulted in any way. If I feel that a 9/11 pic you submit is insulting, I will explain why in the submission comments. Also, This group has been around for more than 3 years! Amazing how time flies, isn't it?