Having images for posts on blogs are very helpful.
We like to think that the main meat of a blog is content/text. But it’s hard to skim over a blog with no images.
Images serve more than to just illustrate. They serve more than to just provide visual interest, they also function as a reference for the reader. We all visit so many blogs and websites, that it’s nice when we can easily recognize what we have already read (yes, there is RSS, but that’s another issue). When there is an image alongside a post of text, the reader can very quickly identify if they read that post already.
Anything that makes it easier for the visitor to read your site will help to keep them as a repeat visitor.