I love inversions and there are many ways to practice them to ensure that you stay safe, esp in regard to the neck.
Inversions have so many benefits including aiding endocrine system and digestion, calming and rejuvenating for the mind or activating!
For me I find the more restorative versions are calming and gently rejuvenating, the more active ones bring a more vibrant energy and clarity as well as a whole new perspective!
NOTES FOR PRACTICE :
CARE must be taken to ensure safety and these are best practiced initially under the guidance of a yoga teacher.
The neck must remain comfortable at all times and there needs to be physical control of the body throughout transitioning in/out of the pose.
A folded blanket under the upper back and shoulders can take pressure off the neck in more active inversions. It's folded edge must end right at the base of the neck...where you feel that knobbly bit!
For the more active viparita kirani or shoulder stand, a test for whether this is safe for you is if you can clasp the hands around your back and roll your shoulders back with ease..such as in full bridge pose. If yes this means you will be able to create a safe support for the neck.
Viparita kirani can be practiced initially as shown below up the wall to get used to the shoulder position and as a warm up.
In headstand the elbows must be no more than shoulder width apart, the head tucked well under and the forearms taking all the weight dynamically pressing down so that the head may be touching the floor but is taking no pressure. This is also best practiced in dolphin pose or against the wall initially to gain the flexibilty in shoulders and to strengthen arms.
Take care and have fun!