Is it a good idea to include descriptive figures/diagrams from previous poster presentations and publications in a statement of purpose?
You have the wrong idea about the SoP. It isn't a survey of your past work. That is for the CV.
The SoP needs to be forward looking, dealing with your goals and plans for the future, both in a degree program and thereafter. Brief statements (phrases, not sentences) about things you have done in the past that support the likelihood of attaining those goals can be ok.
Focus on what you want to study, some sub-field perhaps. Say what your after-degree plans are.
If you just recapitulate the CV, then you are wasting an opportunity.