What I do for the Advent Calendar is send a PM reminder one week out, require a check-in by 3 days out (to say you're on track or to alert the need for a pinch-hitter), and accept submission, well...in theory 24 hours ahead of time, but have been flexible in practice. As the first time zone, I always had to wait until after 6pm on the day to post at midnight Forum time, which usually works well for me, coming home from work in the evening.
I keep all images in private folders on my Imgur, hidden from view to avoid spoilers.
I'm not saying Keep Looking needs to keep this protocol, especially as almost a third of us are essentially now a week out from posting, but it may provide a helpful framework.
I can pinch-hit.
I reserve the right to post extras if I get an inspiration, although those usually come in the form of one of my 'silly doodles'.