Localytics push messaging system works such that each message includes a "payload" that basically tells the OS what to display when the device receives the push (e.g. the text, image, the sound that should be played if any). The default behavior is for the image to simply be the app icon that is loaded on the device (i.e. the same icon that is displayed on the device's home screen). On Android, we also allow you to include a custom icon if you'd like. Localytics is responsible for handing this payload off to Google and then Google delivers it to the device and renders it on the screen.
Once the device receives that information in the payload, the OS is responsible for rendering it -- meaning it takes the information and converts it to stuff you see/hear in the UI (an image, text, sound, etc). Localytics doesn't create any image or render it, so if you are having an issue at this 'rendering' stage, we recommend confirming that your image is designed according to the operating system's specifications, which may change over time. For example, some versions of Android may display certain images in black & white, as described in this Stack Overflow article. You may also want to consult platform-specific literature to determine why the operating system might not be rendering the image as expected.