Are you sure the themes that you are using have BiteSMS? Or that might be just the Chatkit itself.
In bundles it's com.bitesms file.
Look into the Chatkit and open that file. Look at the images and if that matches what you are trying to do then replace those images with the one you want.
Omg you where right the message bubbles and everything were in there lol
So how do I replace it?
Take that Chatkit folder and copy that file to the new theme. Look at my video on how to move it.
Hit edit/top right corner. Click on the folder and bottom right it has a clipboard. Click on that and press copy.
Navigate to the new theme. Do the same. Hit edit. Clipboard/paste. Respring.
Look here. You are going to have to try something. Yes you can add that file even tho it doesn't have one. I do this all day mixing and matching themes to my likings.