In high school I was taught the following useful essay structure:
Introduction: Start general, abstract and universal, and continually focus more and more tightly until you reach your topic sentence, which should be specific, concrete and particular, and which describes exactly what you are going to talk about, in order.
Body: Expand on what you have promised in your topic sentence.
Conclusion: Reiterate what you have just explained in the body.
As far as the body, there are many possible structures. Compare and contrast illuminates one subject by reference to another, showing what is the same, and what is different. Persuasive argues for a specific conclusion. Explanatory explains the details of how something works. Personal connects the topic to your own life. Critical looks for the strengths and the flaws in something. These are just a few of the more common structures. Whichever one you pick, stick to it throughout the essay. Quotes should be used to support what you have said, and should not be expected to carry the weight of the argument themselves. Visuals can be used to supplement the essay, but the text should be able to stand on its own.