You can customize Mobile Favorites pages. However, this requires manually modifying the HTML that generates the Mobile Favorites portal pages.
The files that can be modified are found in the ibi\WebFOCUS81\webapps\webfocus\worp\jsp\mobile directory. These files represent the HTML presented to the user as part of logging in, showing the Mobile Favorites list page, as well as an error page. This can only be done by an administrator.