'https://via.placeholder.com/400.png/09f/fff%20C/O%20https://placeholder.com/', code example

Example 1: create transparent placeholder img

from PIL import Image
img = Image.new('RGB', (32,32), color='white')
img.save('empty.png')
quit()

Example 2: create transparent placeholder img

convert -size 32x32 xc:white empty.jpg