With biteSMS, if you're so inclined you can develop your own themes. You do need some technical skills for that, but if you're up for it, here's some info to get started.
A theme can apply to the biteSMS application, Quick Compose and Quick Reply.
Each directory in the /var/mobile/Library/biteThemes directory on your iPhone holds one theme. A theme must contain an Info.plist file, and contain any images specific to your theme. There are a number of pre-packaged themes already provided in that directory structure when you install biteSMS.
For reference purposes we provide a zip file with an example theme.
You can find the documentation on how to put together a theme in the Info.plist file, contained in the example theme zip file.
The example theme contains all the default apple images that are possible to theme. They are provided for convenience, as you do not need default image files in a theme. In other words if you don't provide a particular image file in your theme, then the default apple one will be used automatically.
Design a theme, then copy the theme directory to /var/mobile/Library/biteThemes on your phone. Theme directory names must be no longer than 15 characters. Change the file permissions to allow both read and execute access, and ensure the owner is the mobile user.
Open up biteSMS, choose the theme and refine it until you are happy!
Here's a few suggestions: