If you want the functionality for directly downloading of your blob files from your xhtml pages, then look in the Seam manual for examples about the s:resource and s:download (jsf) tags.
Thanks Serkan for your help! However when I tried to use <s:resource> tag I got this error:
<s:resource> Tag library supports namespace: http://jboss.com/products/seam/taglib, but no tag was defined for name: resource
I guess I can't use it unless I do an upgrade.
Yeah I guess this tag was available in the later versions of Seam, so you should update or write code in your backing bean for the download functionality (which is not that difficult).