If you chose a sepia toned picture, then you might want to stay away from a brown background when choosing photo birth announcements. In fact, you will want to avoid a monochrome color scheme, as this not only washes out the announcement, but it is also hard to match the colors in your picture and the printing of your announcement.
While you do not want to create monochromatic photo birth announcements, it is still a good idea to use colors from your photo and incorporate these accents into your announcement. These accent colors can tie the whole thing together, and give your announcements a professional feel. The way to make this successful is to choose an accent color, rather than a dominant color that will wash everything out.