It's started now, but that answer would have been no.
You're allowed to use assets made prior to the jam, but only if they weren't specifically made FOR this jam. So if you have old games or assets that you own, you can rip them apart and use them for the jam, but you should not be trying to make assets before the jam starts to use in this jam. That would be working on your game before the jam started, which is against the rules.
