I am sure like me, you will think of better ways to use the images as times goes on. If you find any really great examples, share the link below so we can all see.
Main Image: 851 x 315 pixels
Mini profile image: 180 x180 scaled to 32 x 32 pixels This is the small one directly under the main image.
Apps Image: 111 x 74 pixels
Milestone image: 843 x 403 pixels
Old welcome page app space was 520 wide, but can now be 810 pixels wide, so lots like your website.
I quite like the new look and feel already, and particularly like the fact that you can “pin to the top” a post that you want to promote, for 7 whole days! This then gives you an area to use for promotion without posting the same info everyday and turning your fans off.