There are no limitations to the amount of Media that can go onto the Media Tab.
The amount of Media will increase the database size. 

Before placing an item onto the Media Tab, it must first be placed into the Files folder or you can use Disk Mapping to browse your hard drive (It will not map network drives) to upload the file.  Please note that the Files Folder is not designed to permanently store your media objects, as the space is limited. Once your media file is embedded, you should delete it from the Files Folder.  Each user has only 100MB of storage on the Files Folder.