After finding that some large images were not appearing in my Rails app in Heroku, I opened an AWS account in the hope that they would be shown this way.
I uploaded my images to my S3 bucket and I registered the keys on Heroku, as per the tutorial on the Heroku site. Everything seems to be in place, so I referred to the images using the AWS link:
<img class="d-block w-100" src="https://s3-ap-southeast-
1.amazonaws.com/globalenglish1/EnglishUp-113.jpg">
But this this didn't work so I guess something is missing. The only thing that I can think it might be is that I didn't start my app in Heroku with a Procfile, and I can't find any way of creating a procfile now that I already have my app deployed to Heroku. But I don't really know if this is necessary, it's just my guess.
If anyone can give me any pointers, I would be most grateful.