Yes, you can divide your art in half, but just know that this design will not be as exciting because both halves of the art will feel the same. We want to have differences in our art, so if the design is not particularly dynamic, we could increase another difference, say color, and make that aspect exciting. There are no rules about what you can and can’t do. Try to understand what happens visually when you do divide your picture in perfect halves. It is possible you might want this look. Here is a diagram to illustrate this 50/50 composition and how changing the proportions makes the design more interesting.