Welcome to…
I worked as an art director in corporate publishing for nearly twenty years. I’ve been an illustration educator for roughly the same amount of time. I’ve seen thousands of portfolios. Conducted just about the same amount of portfolio reviews. I have damn near seen it all.
An amateur move isn’t a mistake, per se. They’re often just careless choices, or undercooked designs. To be clear: You’re not necessarily an amateur if you’ve made amateur moves in your illustrations.
I’ve made amateur moves (and will continue to) in every aspect of my life. Plus, there are exceptions to all of this. There are always exceptions in illustration.
That said, let’s talk about five amateur moves I have seen, and continue to see, in the illustrations of aspiring (and working) children’s book creators.