This should do the trick.
misc { disable_hyprland_logo = true }
misc { force_default_wallpaper = 0 # Set to 0 or 1 to disable the anime mascot wallpapers }
disable_hyprland_logo will also disable the hyprland logo too, not only the anime mascots, and will display a solid color if not using hyprpaper
disable_hyprland_logo will also disable the hyprland logo too, not only the anime mascots, and will display a solid color if not using hyprpaper