http://www.topshelfgirlz.wordpress.com - what's that subdomain crap? Buy a domain and put your blog on that - it's not like it costs much.
But to answer your original question - there is no "correct amount" of pictures for a blog post. I took a look at your blog and I think the three thumbnails that you have for most of the posts works well. Four work when they are portrait shaped but as soon as you have four landscape thumbnails it spills over to the next line and looks a bit messy - so I would go for three! It gives them a good taster of the girl but doesn't give away too much and looks neat on the page.
Now back to the more important point of getting rid of that crappy subdomain . . .
