An updated SharePoint Server 2013 Trial image is available in the Windows Azure Platform Gallery. The image is based on the current Windows Server 2012 Datacenter release and includes a complete installation of SharePoint Server 2013 Enterprise Trial patched with the March Public and April Cumulative Updates.
Additional configuration is required to use the SharePoint Server 2013 Trial image include 1) a database server running SQL Server 2008 R2 or SQL Server 2012 2) a server running AD DS.
The current SharePoint Server 2013 Trial image will expire on December 16, 2013 unless activated using the appropriate product key. See also http://technet.microsoft.com/en-us/library/cc263204(v=office.14).aspx.