OK. So I am a total "homer" for our stuff at CohesiveFT. I don't know if any of the other systems out there that help you on-board to EC2 help you elegantly with AMI placement in S3 buckets. If they already do, they have my congrats.
Check this screenshot out.
This is part of our EC2 configuration screen. When Amazon launched their Europe data center at the end of last year - we went live about 8 minutes later with the ability to dynamically create custom AMIs and live deploy them to EC2 USA or EC2 EU.
Still, even after that cool addition, one artifact from the "early days" of Elastic Server, that we had never addressed, was S3 bucket creation, organization and maintenance. We put each of your AMIs into a bucket named the same as the AMI. Simple, but it lead to hitting the AWS "number of buckets" limitation and made sorting in ElasticFox kind of a pain.
BUT above you see how you can select your S3 bucket as part of your assembly instructions. Not only do you get a dynamically created AMI in minutes - but you choose how to organize in S3! Thanks team! This is great!