I noticed that 'The First One' cover that installs the 'exclusive' ambience has also its own ringtones, but:
1) I haven't found a place in the UI that lists them
2) they are probably for exclusive use of that ambience, as they are installed under the ambience folder name (/usr/share/ambience/ambience-the-first-one)

It's a pity, because it seems like the cover changes only the screen background and doesn't let you know the additional properties of the ambience.