NimAWS
When I was exploring Nim in 2017 there weren't many libraries available for it, so I decided to try my hand at writing a Nim SDK for S3 that I could use to upload image and video files from raspberry pi camera kiosks.
Check out the NimAWS readme for more information, it's currently my most popular Github repo and I occasionally get a pull request from someone using it.
While I'd like to take Nim for another spin and maybe update this library as an exercise, I'm sure there are better Nim AWS libraries available now and I'd probably end up building something else.