There are a lot of things you can blog about, once you start getting in to it, you'll find yourself always creating new subjects!
These are just a couple of concepts that we came up with, however the sky is the limit:
Current work: weddings, portrait sessions, travel images, landscape images, whatever you're contending the time
Your most fascinating work: you can pull images from your archives to share
Personal experiences: have a look at The Leader Woman or Tara Whitney for terrific examples of personal blogging
Answers to Frequently asked questions: help your readers get the details they require with some fantastic FAQ posts! Create valuable material for them!
Adventures: people enjoy to live vicariously through their favourite blog writers, so take them on your experiences!
Why you love photography: let them see your inspirations, and they'll feel more connected to you
Promotions at your studio : provide you blog readers unique discount rates, and ensure they learn about any promotions, so they feel like following your blog is valuable!
How you began in photography: your story can truly help them understand who you are as a shooter
Behind the scenes: everyone loves to see how the magic takes place!
Now, take a moment to brainstorm (my favourite word, btw) a few of your very own topic ideas. Merely consider your audience, and what sort of content they would discover fascinating, appropriate, and valuable, and go all out!