I've been interested in casts since I was very young, and as a teenager I also figured out that I like seeing women restrained. Before long, these two interests fused into a love of using casts as secure, comfortable, long-term restraint -- no one would expect to keep someone bound with rope for a month, but someone can easily stay trapped in a body cast for that long or longer.
I don't particularly like full body casts; I prefer types of casts which are very restrictive and inescapable, but still allow the person to move around on their own. My favorite type of (remotely) medically realistic cast is a double shoulder spica (DSS), which starts at the waist, extends up to the neck, then down both arms to the fingers, completely immobilizing the arms and upper body. I'm also a huge fan of straitjacket casts -- these are medically unrealistic and are purely "cast bondage", but they're even more secure than a DSS since a person's fingers and hands are totally encased.
Almost everything I render or post will involve (at least) a DSS or straitjacket cast, so hopefully my renders won't become too monotonous