It is fortunate that Russell made all his theatrical films between 1964 and 2006, because if he was making them today, there are probably scenes and even whole films he could not do.
French Dressing
nothing untoward
Billion $ Brain
nothing untoward
Women in Love
the nude wrestling
The Music Lovers
Nina receiving oral sex from the asylum inmates
The Devils
"The Rape of Christ"
The Boy Friend
nothing untoward
Savage Messiah
unknown
Mahler
"The Conversion" scene
Tommy
Uncle Ernie molesting Tommy
Valentino
Rudolph Valentino's nude scene, featuring full frontal male nudity
To be continued . . .