"Say Cheese!"

It's true, a picture is worth a thousand words. Whether creating a family history book, a pedigree chart, scrapbook (where pictures are essential), or journal, adding pictures, artwork, sketches, etc. add a more complete element.
In a few pedigree charts I've seen (both from long ago, and most recent), pictures were added next to the names. This is especially helpful when you're not familiar with a particular family member. Those great-aunts and uncles from another part of the country or world are much more easily identifiable with their picture by their name, rather than just reading their name on the page. Even though the pedigree chart pictures are just from the neck up and they're tiny, it's enough to see a family resemblance. In a family history book, pictures big and small can add more detail than words can give. Expensive portraits aren't necessary to add in a family collection, although they could be included. Long ago, pictures were taken and printed on tin plates. Sure, they lasted a long time, but they also bent and faded. Regular snapshots work great. An inexpensive disposable camera does the job just fine.
However, with all the technology of digital quality, color-enhancing, blemish-hiding, red-eye eliminating, cropping to size, etc., there isn't much of an excuse anymore NOT to add pictures to a collection of family history.