I have tried to find the answer to this question online without success. The official doc from Google says: "
Screenshots (Required): We require 2 screenshots. Use: Displayed on the details page for your application in Google Play. You may upload up to 8 screenshots. Specs: 320w x 480h, 480w x 800h, or 480w x 854h; 24 bit PNG or JPEG (no alpha) Full bleed, no border in art. Tips: Landscape thumbnails are cropped, but we preserve the image’s full size and aspect ratio if the user opens it up on Google Play app.
To me this is unclear if we can edit the screenshots to add custom art such as add marketing messages for example, or is it forbidden?
Thanks
I think it's okay, a lot of popular game do this, see Cut The Rope or even Angry Birds.