By composition I just mean for instance where the moon has been positioned, it seems too far left for its size and in the foreground more than other items, and where the branch is coming
out of her head. Even though it's an abstract design, some of the objects could have been better placed that's all, to me anyway. Composition is difficult to teach and
often just comes with experience. When you sketch, do it in stages. Do a very rough layout first just with shapes etc until it looks right and then do one or two more
before you do the finished piece. If you're working on tracing paper or a lightbox, try flipping the paper over and sometimes little errors stand out more.
An illustration normally refers to a commercial piece of work that is meant for print or otherwise, something that 'illustrates' a piece of text or a brief, as opposed to a drawing
or a piece of art. There is sometimes crossover of the two though.
I'm just being hyper-critical of course - it's a nice piece of work and I'm sure your friend will be pleased with it.