You are more than welcome to hotlink images directly from the Bannerbear CDN.
However, if you have a high-traffic website, this could cause you to go over your monthly bandwidth limit, leading to overage charges.
If you have a high-traffic website, it's recommended that you host the images directly from your server.
You can find more info on the monthly bandwidth (GB) allowance per plan here.
You will be given 2 weeks notice by email before any extra charges are levied on your account, and we try to resolve this in a friendly way - if you can permanently reduce the bandwidth usage after being notified, extra charges will not be applied.