The more concrete and specific you make your words, the more persuasive you will be to your audience. The same applies to the pictures you show. Recent research backs this up. Students were given short fictional news stories to read:
One story claimed that watching TV was linked to maths ability, based on the fact that both TV viewing and maths activate the temporal love [of the brain]. Crucially students rated these stories to be more scientifically sound when they were accompanied by a brain image, compared with when the equivalent data were presented in a bar chart, or when there was no graphical illustration at all.
So that’s more evidence that pictures add credibility, and that the more concrete the picture is the more it will persuade.