I have filed these as issues on Jira, but I suspect some people here that may know some ideas don't look at the Issue Tracker.
Using the latest trunk from SVN (More or less OS3a4)
1. Uploaded images do not display in cart -- they also do not get resized when uploaded. [http://svn.oscommerce.com/jira/browse/OSC-520]
2. Banner uploads and previews fine but does not display in cart. [http://svn.oscommerce.com/jira/browse/OSC-521]
Any ideas of where solutions may lie greatly appreciated.