Unless you have black speakers, you don't want your frame to be anything but black. The purpose is to enhance your perceived blacks/contrast and to soak up any stray light from the screen. Many use short nap velvet, and a few go with felt. I just painted my back wall flat black.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85