a photo blog idea

I was thinking of creating a photoblog. An adult photoblog to display my collection or rather selections. I could blog about what I like or see in each photo. It sounds like a really good idea to me. However would it be "legal." Not that I would post illegal photos, it just seems likely to not be allowed. You must ensure that the viewer is at least 18 yoa. How would you do that on a blog?

I know just the photo I would use to start it off with. The woman in the picture is truely happy and quite proud. It's titled as found, "stumpy.jpg"