Google Play Featured-Image Guidelines
Description
Creating an Inserted Image that will do an excellent job of highlighting your app requires special design considerations, and locating your embedded image in your key markets is highly recommended.
Not a Real Choice
Although many promotional assets are listed as “optional” for publication on Google Play, we strongly recommend that you manage them as necessary. First, Installed Image is required if your app is to be installed anywhere within Google Play. They are a good idea though; they improve your product page, make your game or application more attractive to end users (and will probably be considered included by our editorial team).
There is no choice in size, either; should be 1024 x 500 pixels.
Do and Do Not Do
Your image is not an ad, it is a joke. It is a place of bright, intelligent advertising images.
Clear background colors work very well. Black and white are problems because those are the backgrounds used by mobile device and web versions of Google Play.
Limit text to the name of your application and perhaps a few descriptive words. Anything else will not be read on phones, anyway.Download