There are many third-party apps available on the App Store that allow you to change the background of your text messages on iPhone. Here are a few popular ones:
|Color Text Messages+||This app allows you to customize your text messages with different fonts, colors, and backgrounds.|
|SMS Backgrounds||This app offers a wide range of backgrounds and themes to choose from to customize your text messages.|
|Bubble||This app allows you to customize the bubble colors and fonts in your text messages, as well as add backgrounds.|
|Textizer||This app lets you add backgrounds, fonts, and colors to your text messages.|
To use these apps, you will need to download them from the App Store and follow the instructions for customizing your text messages. Keep in mind that some of these apps may require in-app purchases for certain features or content.