When I choose a frame to coordinate with a specific image, I consider the "flavor or feeling" the image portrays. Does the image work well with one of my wood-grain styles or does it lean toward a more elegant gold or silver leaf or maybe the mahogany?
Of course, I also need to consider the colors involved in both the image and the frame. I look for a color in the image - either a major one or a minor one I want to accentuate - and then chose a frame color which sets off and enhances this subject color.
When you do not want to add a colored frame to your decor, you can choose the black. Black will coordinate with - and compliment - any of my images; plus the black is a bit more formal.