Just me...but there isn't much "plain" about that house. Not sure the window needs much more. Full disclosure...I am not a designer...just an exterior remodeler and an amateur tattoo artist (kudos is folks know that reference).

If you want to to make it stand out more id paint the trim a different color than the siding. the trim color of the other windows is what id normally suggest but i dont think that color goes well with the brown paint around the window. if possible repaint all window trim a color that coordinates a bit better.