I think I could get quite carried away here...
I really (REALLY!) enjoy your pictures of Caroline, Master Kurt. Slave humiliations are probably my favorite fantasy. One never realizes how intense situations can become due just to little details, e.g. Caroline often being the only person in the pics without any clothes, until one experiences them in person. I am normally not shy about being naked in front of others, but the first time I ever knelt naked in front of my (ex-) girlfriend and a friend of hers was one of the most intense sexual rushes I have ever experienced. And, when I was ordered to lick four not-so-clean female feet... Unbelievable. And I don't even have a "thing" for feet!
Many of my fantasies revolve around being used as a toilet like Caroline. On occasion, my ex- used me as her pissoire for an entire weekend. Things progressed to where she used my tongue as "toilet paper" - not only for piss... (was Caroline ever used like this? You mentioned her being used for extensive analingus..) She always threatened to continue my "education" as a toilet, but we never got that far. Sometimes I wonder. At times, she would also require me to clean her toilet bowl with my tongue. Its amazing how little of a toilet can be reached with a tongue - even with vicious contortions.
One of my other extreme humiliation fantasies is to be used as a "sexual servant" by a couple or several couples - especially being used to clean the genitals with my tongue after intercourse (this is extreme for me because I don't consider myself truly bi, it is more the humiliation and degradation that would get me going - strange, huh?). You mentioned that Caroline would service whoever was present, was she used for "cleaning" in this manner also?
One of my present female acquaintances (sub also) described a scenario that she found appealing. We were visiting an old farm (no longer in use) and she described her fantasy of being chained just by her collar in an old dirty stall while outside in the yard a party took place. One by one (or more) the guest would come in and use her in whichever manner they liked. To this I added the idea of being used as a toilet also, increasingly as the party wore on. We were both quite turned on at the end of our visit without anything having transpired.
One other thing that adds to the humiliation is an age difference (probably because it looks more like pure service/slavery rather than love). I really enjoy pictures of a younger (no kiddies!), good looking slave servicing an older master/mistress. The picture of Caroline being used as a pissoire by Helen is terrific (I hope Helen doesn't read this!). I'd love to see more pics of Caroline servicing older looking mistresses (especially oral service of any kind).
Thanks very much for posting the pics you have up to now, and please continue!