Novels have much more space than short stories, which gives you more leeway with the number of characters you can include. Even 'furniture' characters can be described and given speaking parts to develop background or atmosphere.

All writers, in all viewpoints, must choose which information and scenes will be presented, and in which order. In that sense, the author is always represented as a point of view in a work of fiction. His hand can always be detected by the discerning.

For the professional writer, stories must be presented as a series of individual scenes, each one dramatized with dialogue and telling descriptions of who is present and what they're all doing.

Nancy Kress Quotes