I have just taken a look and for some reason images shared from Google Drive seem to fail with an HTTP 403 status, I am not sure why this is but it looks like other images work ok so it looks like it could be something on the Google side or maybe the way the image is shared.
I just used a couple I found on Google image searches from random sites and they all appear to work. It could have something to do with image preview urls rather than direct urls.