People keep finding ways to bend the rules, lol!
While you're technically rendering a game to 64x64, you're rendering a scene around it as well. It's generally been agreed that black empty borders are OK, and the rules state you can render a graphical border if it's on the web-page rather than in the game... I mean, you can do it if you like, at the end of the day "authenticity (use of 64x64resolution)" is a thing people will be rating on. so people may interporate that in your favour, or not... ;)