For example, this image I deleted, but its url still works (which is good, I need it to work forever)
how long is it going to work for?
FYI, that link doesn't work for me. Images on the CDN do not hang around very long after being deleted so don't rely on them being accessible long term.
Also note that you posted this in the fourm section dedicated to Shopify Scripts.
Be sure to post in a more appropiate section next time ;)