I agree with anthkris. Think of your text story like a real physical book. In a typical published novel, illustrations are usually dispersed when you need to show something in more detail that descriptions alone don't do justice. Like, say if you were describing a certain scenario in a beautiful landscape but use a comparison that might seem foreign to some readers. For a small effort,viewers don't necessarily expect anything close to perfection. A game jam is more of an idea showcase. As long as we the readers get a general grasp as to what you would do if your piece was completely finished and polished through much more hours of work, I feel it gets the job done. Consider a certain style of illustration you like. Maybe something with exaggerated borders, super-deformed features, simply drawn faces, or even a more basic color scheme or layout. It doesn't really matter how much effort you put into it, as long as it fits the style of your game and looks aesthetically okay it should be alright. You seem to be overthinking the whole process a little bit. With a good reference in mind, you should be able to convey what you need to. There's no shame in that whatsoever.