I want to change a chat room wallpaper.

You can set up a chat room’s wallpaper screen.

1. How to set up whole chat room’s background 
Press More Options(…) - Settings (on the upper right side) - Wallpaper Settings.
You can either choose a picture from album or take a picture with the camera to set up the whole chat room’s background. Or press Choose Wallpaper to select one from the backgrounds provided by Lysn.

2. How to set up individual chat room’s background 
After entering into a chat room you want to change the background, press More options (on the upper right side) - Settings (on the lower right side) - Wallpaper Settings. For open chat room, you can change its background on More Options on the upper right side - Settings on the lower right side - Chat Room Settings Tab - Wallpaper Settings.