Consider providing multiple images of your 'pictures'. Display the appropriate one depending on the dimensions of the screen your app runs on (see Screen Size .
In Screen.Initialize, determine the screen dimensions the app is running on. Based on the dimensions tell your app to use a high or a low resolution version of your 'picture'. Mimicking the behavior of Android Studio apps should ensure large high quality images on tablets and clear, smaller images on small phone screens. Make your app behave like apps built using using Android Studio.
Let us know the results of your experiments. Provide a screen capture to show how you improved the images. Good luck.