Believe it or not there is a lot more to nude photography than pressing the shutter release once a model has their clothes off. Lighting and composition becomes far more important as there are often fewer props to hide poor photographic technique.
There are also a number of sub-divisions within this group from a figure study to erotica, which all have sometimes subtle differences from each other.
To model for this style your age, size and looks are not as important as the ability to relax, so if you are 50 years old or 200+ pounds I will still want to photograph you.
These are just some of the variations that fall into the artistic nude category.
This involves capturing the body either in motion or at rest to capture the versatility and variety in the human form. This could involve photographing an athlete or dancer as they exercise or prepare, or it could simply be someone reading, enjoying a moments reflection, washing, relaxing or stretching.
Difficult one to describe in words but the mood is soft and gentle. It's possible that the location or props will take precedence in this sort of picture, so imagine a woman nude apart from a long hooded cape, on a bench in the centre of a maze, lost in the words of the book she is reading. I'm sure you can imagine many more scenarios in different locations, costumes or time periods.