Pewter frame, it looks good and it's a fun word to say ... Pewter pewter pewter :)
Red, I like red frames.
Last time I painted window frame it was white. Im guessing it would depend on the color of the walls and everything...
I personally like vintage picture frames. For make them look vintage, I prefer off-white, cream rustic or dusty gold colors. They are perfect to give it a vintage feel. Last week I got this vintage frame from here https://www.rajrang.com/home-decor/photo-frames/vintage-hand-painted-gray-wood-and-metal-photo-frame.html