A helpful thing before starting an illustration or a pattern is to decide where it fits on what I like to call "The Reality Scale". Making decisions beforehand if your work should be very representative or very abstracted or somewhere inbetween helps you set the tone before even putting pen to paper. It helps you refine your moodboard or inspirations in a relevant way.
It also helps to communicate this with your client when embarking on a new commission. Have examples ready from your portfolio and make sure you are both on the same page.