^ here is the initial template.
How it works is the first person takes this image, makes changes and then posts the results. The next person uses that as the start point, makes their changes, and then posts as a new image, and the next person uses that image as their start point, etc.
Too complicated? Then don't bother
Obviously there could be overlap, but tough.
You can do anything, so long as it is within board rules.
I will update my sig each morning, based on the current image.