If you are like me and have hacked your iPhone up pretty well, and you can’t stand the lack of good SMS bubbles, here’s a little hack to set yourself up.
1) SSH to your phone as root (with the alpine password)
2) cd /System/Library/PrivateFrameworks/ChatKit.framework/
3) Make a backup of the Balloon_1.png & Balloon_2.png to /tmp
4) From your machine, scp the replacement files over : scp Balloon_1.png root@$PHONEIPADDRESS$:/System/Library/PrivateFrameworks/ChatKit.framework/
5) Repeat with Balloon_2.png
6) Restart Springboard