What's the purpose of multiple asset sources?
You should use the bucket directory structure for the different asset types; you're right, they are all coming from the same source, really, so separete asset sources wouldn't be correct.

Another asset source would be simply another bucket, or another type of source such as Google Cloud or Rackspace.

You could have an asset source called Web S3 Assets, which connects to your bucket. 

As an example, you could have these directories within that bucket for all the types of assets you need to store.


&lt;bucket-url&gt;/images/icons/
&lt;bucket-url&gt;/images/illustrations/
&lt;bucket-url&gt;/images/screenshots/
&lt;bucket-url&gt;/videos/marketing/
&lt;bucket-url&gt;/videos/support/


Use Assets Fields to force usage, upload restrictions on these directories.