nextINTERACT shelf icons should be no bigger than 208 x 256 (w x h) pixel at 72 dpi.
myINTERACT tile images need to be exactly 656 x 476 (w x h) pixels at 72 dpi.
We recommend to use JPEG files for myINTERACT tiles due the small file size. Also supported are animated GIF images, to create an effect of animation.
For nextINTERACT PNG files can be used to get a rounded borders effect if desired.