So I would not be breaking the rules if I gathered my art and hacks together ahead of time? For some reason, I was under the impression that those would have to be done inside the one week window and I've just been planning them out in Notepad.
I don't think so. To be fair, though, the rules are whatever you want them to be, as it's an individual challenge.
When I did the four-day challenge, I started with one of my previous modules as a base that already had hacks and artwork added to it. I think gathering or preparing art in advance is fine. The challenge (at least to me) is really about putting it all together and getting it all into a working module in seven days once it begins.
If you think it's not in the spirit of the challenge, you can certainly wait. As I said above, it's an individual challenge and I believe everyone's journey will be different.