looks about the right proportions / wing shape for S. tenebrosa. Sasunaga longiplaga has longer, thinner looking forewings, though the pattern on both species is similar and both have very variable colour forms.
Never mind about the background, so long as it doesn't detract from a clear photo that aids identification. I have many photos of moths on similarly uniform backgrounds - mostly from specimens photographed on a white sheet at or under a light trap. Worry about getting the picture perfect image later!