All our in-app images have a ratio of 16:9. The largest Image in the app is 1920x1080. You will only be asked to upload 1920x1080 images and we will do all the scaling and fit for you.
When ingesting content into Applicaster Admin console, ensure the image key is: 'tvml_image'. More details regarding VOD ingestion.
As for the app icon size, you will need to supply it in two sizes:
Small size - 400x240
Big size - 1280x768
The AppleTV icon also has an option that allows you to split your logo into layers. The separation between layers, along with use of transparency, creates a feeling of depth. As someone interacts with an image, higher levels elevate and scale, overlapping lower levels further back, producing a 3D effect.
For more information on layered images, please check the AppleTV human guidelines on Layered Images
You need to follow and maintain AppleTV design guideline for the icon size in order for Apple to approve your app in the AppStore.
You can find more information regarding the new AppleTV design here: Apple new Human interface guideline