JGD-FallSunset is a dark GTK theme collection with an orange, brown and blue color scheme. An optional icon theme is also available from the GitHub repo!
Download and Installation instructions for the themes and icons are at GitHub: https://github.com/jgpws/jgd-fall-sunset.
About the wallpaper
The wallpaper used in the background is titled Sunset Birds Flying. It is at Pixabay: https://pixabay.com/en/sunset-birds-flying-sky-colorful-100367/.