Daily or Weekly Themes

Do you like doing themes for certain days of the week? For example, every Wednesday posting a picture. The only one I do is my comment of the week. I always feel like having a theme will box me in, even if I don't do one for every day. However, I know lot's of bloggers who have a theme for almost every day. The idea is that it gives you a starting point, and from there it is easier to come up with ideas. What does everyone here think?