Only one answer: take the time in your research. Choose an artist who produces a style and images related to what you want. Be clear in what you want, even if it means making a draft yourself (even if it’s ugly, who cares, it’s just to place the elements at your convenience.) The less indication you give, the more the degree of freedom for the artist is high, the more you trust him the more it will resemble his style. If it is his style that you want then leave it as free as possible, if it is your idea that you want then give a maximum of indication and photos.