There are a few more tones can be played but are not listed in the programming guide
tn_ringback -- Plays a ring back tone
tn_congestion -- Play a congestion tone
tn_stuttdial -- plays a stutter dial tone
tn_intercept --plays a intercept tone, like busy tone
For example I have to use "leg setup $dest callinfo" for a reason
I don't provide incoming leg, so when the ev_alert or ev_progress coming in script won't be able to ring calling party.
At this moment I can use "playtone leg_incoming tn_ringback" to provide local ring back"
Hope this can help someone when they need it.