AFAIK= as far as I know.
To change the text bubbles you would have to replace the following images with your own images:
Balloon_2@2x.png = white bubble used for all received messages (SMS and iMessage)
Balloon_1@2x.png= red bubble used for outgoing SMS
Balloon_Blue@2x.png= blue bubble used for outgoing iMessages
They also started using a green Send button for normal SMS and a blue Send button for iMessages. Those files are:
SendButton@2x.png = Blue send button for iMessages
SendButtonPressed@2x.png = Blue send button for iMessages (pressed)
SendButtonGreen@2x.png = Green send button for SMS messages
SendButtonPressedGreen@2x.png = Green send button for SMS messages (pressed)