Some of them are not in fixed forms. They can shapeshift and change their appearance based on your needs and experiences. Its not uncommon for spirits to approach as male or female based on the conjurer, and when this occurs it makes gender-based references very difficult.
Instead, it is often more worthwhile to describe a spirit by its nature and the nature of those experiences you have with said spirit. If, for instance, a spirit consistently manifests as an intelligence felt over the shoulder with a kind disposition, guidance given, and you feel a surge of energy, that’s a very good thing to reference. It gives others something to expect and a yardstick by which to measure said entity.
Imagery changes a fair bit, but the experiences of such powers can often be rather consistent. ;)