Help with timber picture frame finish

Hi All,

I am currently working on a picture frame for a photo I took, and I am unsure what type of finish I will need. The frame is timber, and so far I have used a grey primer, then painted it white, then painted black over the top of that. I then sanded some of the black back so that some of the white underneath is showing through. I am trying to get an older style look as the photo I have is black and white. I would like then to put some sort of sealant over the top of the paint, but I don't want a glossy finish rather something that prevents any of the paint coming off but you can't tell that its there.

Any advice on what I should use?

Thanks in advance,Tim.