Images can make your blog look more interesting. I don’t have enough statistical data to prove this, but from my experience books (for example) without images are heavier to read than books with images. Articles with images are lighter than articles without images. I presume a blog without images is duller than a blog with images.
I don’t spreading images much all over your blog, but use them sometimes. Content of the blog is the number one issue that matters – of course – but interesting content with interesting images is better than interesting content only, right?