Communicating in pictures is the first form of writing-on-paper primary teachers address. The power of more picture details is that students then have more details to label. The more they label, the more they can write and develop. This produces young writers who can do more than draw a picture and write a single sentence. They can draw a picture and write numerous sentences!
But don’t just tell students to draw with details, teach them how. There are several explicit lessons you could address within these first weeks of school. Take your time as you introduce these new concepts in lessons. Each idea might require more than a one-day mini-lesson.