Yes it is indeed good to elevate your feet while sleeping.
When you elevate your feet and legs while sleeping it can help you get a better nights sleep and you reduce your risk of blood clots or leg or foot numbness when sleeping.
When your legs are elevated while sleeping the blood can flow much better and more easily through the blood vessels in your legs because of the gravity allowing the blood to flow much better back to the heart.
Your blood is constantly going through your heart, brain, leg blood vessels, arm blood vessels and all the other blood vessels and the blood flows through those veins, into your heart and back around again.
The less resistance the blood flow has the easier the blood can flow so that you feel better and the blood will not clot as easily.
You should also elevate your legs when laying on the couch or in a chair relaxing watching TV or just lounging around as it can and will make you feel better.
I elevate my legs 12 inches when sleeping and I always feel better and get a better nights sleep.