A hard reflecting surface, like your OLED screen centered between the speakers is not necessarily a bad thing. This often actually helps to create a sense of focus or solidity of the center image. You can try covering it up with something like a comforter to see if that helps; if it does not, don't worry about it. You can also try diffusion on the rest of the wall behind the speaker, but that too may no be necessary. There are commercial panels made by companies like GIK that may improve the sound and can be covered to your liking visually (including blowups of photos that you like), but before spending that kind of money, you could try othe decorative "treatments" like large potted plants (real or fake).
Good luck on your endeavors.