Ghalib, to where will they be able to import the file names and descriptions? mojoPortal doesn't store this information in the database.
Image references are only stored in the database when they are used in content. If you want to create content automatically (at install time) and use the images in that content, that is a different scenario. You should review this documentation for that: http://www.mojoportal.com/configuring-initial-content.aspx.
You could also create "Content Templates" but there isn't any documentation on how to do that programmatically, yet. So you will have to review the source code to figure that one out.