The media files available on the WUI for each user is user specific, It will show the media file(s) available under "C:\IPcelerate\IPsession\wwwroot\users\<UserID>\messages" folder e.g. if you want to assign the new media files under "Administrator" user, then copy the media files in "C:\IPcelerate\IPsession\wwwroot\users\Administrator\messages" folder. The media file format should be 8-bit-mono wav/au only.

Let us know if you have any further queries or concerns.