Vanessa Morgan has pictures with him and others on her Instagram (#1, #2, #3, #4, #5 with Laurence Fishburne and his wife, Gina Torres). Michael Mando has one as well. (Pics from Twitter users Dion Johnstone (#1 & #2) and Melissa DiMarco).
UPDATE: 04/04/2013 - 5:05PM
Another photo below of Atticus courtesy of theartsscene.ca (who will later post interviews with the cast from the event). Click on photo to enlarge. Later, Vanessa Morgan also posted another picture on her Instagram.
UPDATE: 04/05/2013 - 8:35PM
Four more photos of Atticus Mitchell, the first three from theartsscene.ca (the bottom one CTV News Toronto) with Dru Viergever, John Tench, Michael Mando, and Lisa Berry. Click on images to enlarge.
Another photo of Atticus and The Colony cast (Dru Viergever, John Tench, and Lisa Berry) from their official Facebook page. Click to enlarge.
UPDATE: 04/13/2013 - 8:55PM
Three more pictures of Atticus Mitchell at the industry screening of The Colony at the Toronto International Film Festival (TIFF) Bell Lightbox on April 4, 2013 (from The Colony Official FB page); with Vanessa Morgan, Michael Mando, John Tench, Dru Viergever, Kimberly-Sue Murray and other cast/crew members. Click to enlarge.
UPDATE: 04/17/2013 - 5:05PM
I have six more photos of Atticus Mitchell at the Toronto premiere event of The Colony on April 3rd, from the AP website. I tried my best to find a way around their 'over-watermarking', no avail unless you have an account with them and can purchase these. Photos below by Arthur Mola/Invision/AP. Click to enlarge (but not by much).
See also: Atticus Mitchell Chatting About The Colony (view also on YouTube)