This should be possible to do, though not with WP-SimpleViewer (the SimpleViewer plugin for WordPress).
You would need to first create a gallery (perhaps with a single dummy image using svBuilder-Pro) and manually edit the gallery's XML file so that the imageURL and thumbURL entries point towards the images in your Amazon S3 bucket.
You would then need to embed the gallery in your WordPress page or post using the baseURL method of embedding documented here.
When uploading the gallery folder to your web server, I would recommend keeping it outside your WordPress installation (to help keep things separate from each other).
Also, I would recommend using absolute paths in your embedding code (to the 'simpleviewer.js' file and for the baseURL itself) as it may be difficult to determine relative paths in a WordPress installation where pages are created dynamically.
(Make sure, when entering the embedding code into the body of your WordPress page or post, that the method of entry is 'Text' rather than 'Visual'.)