Any mirror service allows exact matching path will work. SimpleCDN Mirror bucket and Amazon S3/Cloudfront are tested..
Please check my post: How to copy selected files to Aamazon S3 Cloudfront
Please check my post: How to batch process js and css
Please check my post: Correct SimpleCDN pre-URL and CNAMEs
If you have more than 10 items on a single page, you should. However css images refered in a single css file will be loaded from a single destination.