Currently application developer can have custom file upload template by calling Fileupload#setTemplate(String uri) and if required extending FileuploadDlg to manage new custom template. If the custom template requires some additional parameters to customize template before showing to end user there are few ways to achieve this
1. Set them in desktop using Desktop.setAttribute() & retrieve in extended FileuploadDlg (disadvantage is - need to have additional method calls for setAttribute() before each Fileupload.get() )
2. Set as arg in execution before calling Fileupload.get() & retrieve in extended FileuploadDlg(disadvantage - same as 1)
3. Use a service to retrieve in extended FileuploadDlg (need to maintain hard reference to service in extended FileuploadDlg class)

Possible enhancement could be: Have a protected method in Fileupload class that can be overridden to add additional parameters for template.