As of right now, this feature isn't available. The primary purpose of blog entries are to be industry news, for which I don't think it's a priority to be able to include image attachments. In the long term, I am thinking attachments will be available, but it is a low priority for me right now.
Shame. I would have liked to have done a blog regarding 3d composition and ray tracers - Using diagrams would have been nice. Links don't have the same effect. Never mind. Maybe I'll start blogging next year when the feature is implemented. :)
Oh okay. I'm not going to work on the blog script for awhile because it appears as if the vBulletin developers will be putting out an official blog script in the near future, and so I want to see what that's all about before putting much more work and effort into my own custom blog script.
While the blog script I've written is 100% based on the vBulletin framework, I am willing to be that a blog script developed by the vBulletin team for vBulletin integration will most likely incorporate most of vB forum features such as attached images, etc. already ... and I don't want to put time into redeveloping the wheel right now.