There are specific requirements for Android banner:
- ≤ 450px wide;
- ~2:1 aspect;
- the image should be centre-cropped.
- the link should be HTTPS only.
Please note that banner behaviour is entirely controlled by the Android/User interface! Pushwoosh SDK by default contains the specific method for showing the pictures in the push, but the handling of it is passed to the operating system. For instance, the inconsistencies may be observed on some devices with custom UI (e.g. Samsung TouchWiz and HTC Sense).
Also, please note that to be properly displayed, the message with a banner should be the very first in your Notification Bar, otherwise some parts of it (e.g. header or content) might be missing.