I though that at first too. But then I thought it was too quick to have the entire cast already when they just made the announcement.

I found it on deviantArt. Here's what the artist says
Just a bit of fun. I cast the poster with who I thought should play each character for the film series. Reference for each actor was compiled through google and IMDB.
http://ostrander.deviantart.com/#/d2yzdr5