Changing the SMS background, where is the stock image?

[billinaz]

I just got an iphone after years with a Samsung Galaxy note. I went to change the background of the SMS messaging app but I don't know where that image in in IOS 8.

Does anyone know where I can change that image?

 

[Europa]

Install Messages Customizer in Cydia.

 

[billinaz]

I tried it, but it keeps causing my messages app to crash. If I knew where the image file is now I would just change that......