<p>Is it ok if I include, say, sentences without verbs if I'm trying to maintain a certain rhythm in my essay? Assume the rest of it is grammatically proper.</p>
<p>It depends on the context and how well the technique works. If it improves the flow/feel of your essay and is clearly intentional, I don’t see why you shouldn’t include it. Get a few people to read it without telling them about the grammar beforehand and see how they react. If they don’t seem to get what you were trying to do, you probably should revise it.</p>