>I'm less bullish on images, unless they are profoundly relevant to the text. Illustrations for the sake of having illustrations are no bueno in my opinion. You want to reduce distractions and visual noise.
I'll respectfully disagree on this one. You can overdo images, but I think readers find a wall of text intimidating and visually too boring, but this is a matter of taste.
>Images should above all never be funny.
I strongly disagree with this. It's like saying a technical blog post should never have jokes.
Why should an image never be funny?
I think you absolutely can mix humor and useful technical insights. xkcd is probably the best example, but there are lots of authors that complement their writing with humor, both in images and in text.