This page covers the icon image specifications for 2016 models.
Even though submit only1920x1080 size of icon images, 1:1 icon image is made automatically. However, if you don’t like the 1:1 icon image produced automatically, you can change the image by clicking the button. the button is shown only after the original size 1920x1080 pixel image is submitted.
The spec of Screenshot is also changed. 1280 x 720 pixel or 1920 x 1080 pixel of screen shot image is only allow to be registered. If you registered 960x540 pixel of Screenshot image previously, you will be asked to register larger than 1280x720 pixel of image for version up in 16 model groups.