Jeff Atwood's blog is one of the best out there. But he says you don't need random gratuitous images, and they're actively counterproductive. I absolutely disagree.
Jeff's a smart guy, but he also uses Windows. You can respect his intelligence and still disagree with his conclusions from time to time.
First of all, what random images do in a blog is the same thing "random" facial expressions and gestures do in a conversation - they contextualize what the person is saying.
Context matters. Context matters immensely.
The idea that technical materials should be dry and devoid of personality is old-school bullshit.
Read up on Kathy Sierra's Head First series and you'll discover that actively engaging the part of the brain which recognizes facial expressions is the easiest and most powerful way to accelerate learning.
Do you want to learn fast? I do.