To use ringtone support, create file containing ringtone:

echo ':d=4,o=5,b=100:c.,c,8c,c.,d#,8d,d,8c,c,8c,2c.' > /tmp/delme

[This is so-called RTTTL, see http://overtonez.co.uk/info/rtttl.txt]

then set it on the phone

gnokii --setringtone /tmp/delme

. Good source of ringtones is http://overtonez.co.uk/ or for example
http://www.micromelody.com/.