Where

Settings → Chat Settings (or Appearance) → choose a wallpaper, globally or per chat. Desktop also offers patterns and a theme editor.

Types

  • Official patterns that adapt to light and dark themes;
  • Solid colours and gradients, light on resources;
  • Custom images with blur and brightness controls.

Advanced

  1. Export a theme file on desktop and share it;
  2. Motion wallpapers add a subtle parallax effect;
  3. Give important chats their own wallpaper for quick recognition.