New wireshark has decompressor to decode compressed SIGCOMP SIP Messages.
I couldnt find any sample SIGCOMP Message on internet so putting link where you can download SAMPLE registration message using SIGCOMP.
http://www.mediafire.com/?ah2vx6245mts7tr
Sigcomp Packet was generate by Linking tinySIGCOMP in chan_sip of asterisk .
One Asterisk was registered as client with Another asterisk and sip messages was compressed.