I've been keeping a record of commission types and what I've learned from each category of client, and want to share the observations.

Gaming clients (indie games, tabletop RPGs): typically the most visually literate. They communicate in art vocabulary. They're often designers themselves and give useful feedback. The budgets at the indie level are modest but the creative latitude is wide.

Book cover clients (self-publishing authors): highly variable. Some authors have a clear visual vision; others have a concept but can't articulate it visually. The creative challenge is often translating a narrative concept into a visual that works as a book cover before it works as an illustration.

Business clients (logos, brand illustration, social media content): the most practically demanding. They know exactly what they need (brand consistency, specific message) but sometimes can't articulate it in visual terms. The brief needs to be exceptionally clear before work begins.

Personal commission clients (portraits, fan art, gift art): the most emotionally invested. The work is personal to them in a way commercial work is not. This can produce the most satisfying completed projects and also the most challenging client management situations.