All post by specific authors on regular page

So I’m finding the auto-generated author page limiting for my purpose. What I need – and what I hope someone can point me in the right direction for – is either a way to add a featured image to an author page (I’m not referring to a gravatar or the like) or way to feature all posts by a specific author on a page like one might do with a blog page.

At issue is a theme that allows a featured image for category archives but not author archives.

I realize I can just assign every post by an author it’s own secondary category, but then posts then have two labels on the front page and not one.

Make sense?

Thanks in advance.