I need to add this restriction (i.e. each user has to save ejs file under his/her particular directory) to prevent more than one user upload different simulation with the same file name (it would overwrite previous file which will produce some trouble).
The upload ejs jar file only support ejs source file being save under users/ sub-directory.
This will also prevent confusion when two user share simulation with the same file name.

P.S. the problem you reported:"missing the thumbnails image" is fixed now.  :D