how do i block some videos from sharing?

Unfortunately no - on the old AppleTV unticking items in iTunes prevented them from being shared.

It's not just movies, I have music/album covers I don't want streamed.

Send feedback:

http://www.apple.com/feedback/appletv.html

in pref sharing in itunes

you can set it to share your whole lib

what you need to set it to share is a playlist where you add the stuff you want to share

If the movies are purchased movies they will have ratings, use parental controls to restrict movies with specific ratings.

Rudegar wrote:

in pref sharing in itunes

you can set it to share your whole lib

what you need to set it to share is a playlist where you add the stuff you want to share

Does that work for Home Sharing?

No

That was my assumption.