Trying to find a wallpaper using red and black and thought to look at flags on Wikipedia. I wanted vertical stripes with red on the left. Belgium was close, (https://en.wikipedia.org/wiki/Flag_of_Belgium) but it had red on the right and was also too bright. Thats why I Black Mirrored it.

Actually, I used Inkscape to horizontally flip it, ungroup the objects, and then choose darker colors.

I left the objects ungrouped if you want to change it further.