[ronie]

1) the script doesn't handle images, kodi does. the script only creates a simple picture playlist file and asks kodi to display the images one at a time.
i have no idea if there's a limitation on the pi, but for kodi it shouldn't matter.

2) if the resolution of the image doesn't match the resolution of the screen, then either parts of the image will be cropped, or black bars alongside the image will be shown.
it depends on whether you've enabled 'scale images fullscreen' in the screensaver settings