It's not too late to join! See the above image for details!
Quoted from 's blog:
"The idea is a collaboration picture, and depending on the response we'll do either every character in the game or every mask that Link collects. If we get more than 24 people who want to participate then we'll do characters, if not, we'll do masks. If we get enough to do both characters and all the masks we'll do that. We'll also need people to create the background, and exactly what it will look like depends on the size of the response.
The finished collaboration will be featured on the Operation Moonfall Facebook page!"
So what are you waiting for? If you're interested, head on over to the collaboration blog and send in your request!