Cloudformation template - unrecognised resource type

Here is a list of resources for Cloudformation AWS:EC2 https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/AWS_EC2.html

there is no AWS::EC2::Image resource, that's why you get an error unrecognised resource type

If you need to create a new image via CloudFormation, consider using AWS::ImageBuilder::Image

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-imagebuilder-image.html

Hello.

The cause of the error is that the resource type "AWS::EC2::Image" does not exist.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/AWS_EC2.html

Currently, I think it is necessary to use ImageBuilder etc. to create an AMI with CloudFormation.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/AWS_ImageBuilder.html

ec2 instance create a snapshot and saved to s3 bucket

You mentioned that you saved the snapshot in an S3 bucket, but how exactly did you save it?
I think the snapshot data is stored in S3 managed by AWS, so I don't think it will be output to S3 managed by the user.
https://repost.aws/knowledge-center/ebs-copy-snapshot-data-s3-create-volume