Highlighting key areas such as a colour palette or the stroke weight are obviously vital to creating solidarity across a style. But outlining information such as the values attributed for the illustration style, or what you want to achieve from having them on your platform are also just as important.
… values and a high level rationale as to why you need illustrations is key to outlining your style. Having a consistent style will obviously create an overarching style that will create harmony across you illustrations. It will mean that various illustrators can tackle illustrations on the same platform safe in the knowledge that their work will look part of the family.