Depending on what it is you are trying to achieve – lots of pictures can be a good thing. You can write a paragraph explaining something badly, or just stick a picture in with an arrow pointing to what it is you are on about.
If you refer to a picture, don’t have the text going over a page, if it can be helped.
Don’t put a pic on one page when the text referring to it starts on the previous or next page. That kind of thing.
Just imagine yourself as the end-user and having to use that doc for the very first time. We often used to get people from other departments to use our SOPs (Standard Operating Procedures) once they were about to be released to see how much ‘assumed knowledge’ we had added into the document.
With regards to style – clear & easy to follow, is about all I can add.