There are many different ways you can do the headstand. You can do the headstand with your legs straight like my friend Kristin (girl on left) or wide like my legs.
Either way both of these poses are good for your lower spine and helps with blood flow.
We use the wall for added support but if you are more experienced then you don't have to use the wall. I'm sure someday I will get there without the wall.
As of right now, I'll stick with the wall. It also helps with abs bringing your legs up and down.
Here is a good tutorial video on the wide leg headstand.