So I'm new to ecs/ecr, but it seems like I have to name (with a tag) the image after the repository name in order to push that image to the repository.
So my question is: Is it intended that the user (me) would ONLY be pushing a single image and any associated versions of that image to a single repository in ecr, thus creating ANOTHER repository if i need to push a completely different image?
basically, one repo for nginx, one repo for postgressql, etc.
Yes. And also, possibly, no.
You push images to ECR. How you configure your image is up to you. Ideally, you'd have an image with a single responsibility, but this is your decision.
If you have multiple images, you push to multiple ECRs. If you have a single image doing many things, you can get away with a single ECR.
You can also push multiple images to the same ECR with creative use of tags (e.g. having the "image name or flavour" in the tag using your own naming convention.