If you intend to change it to other image, simply modify the input file (profile.png)

logo_display = Image.open('profile.png')

To resize the overlay image, modify the following

logo_display.thumbnail((60, 60))

For changing the positioning of overlay image, play around with the following

logo_pos = ((img.size[0] - logo_display.size[0]) // 2, (img.size[1] - logo_display.size[1]) // 2)