The Love Chain is one for instance, it can be done in different ways where the one only receiving could either be on her back or with her back to the one in the middle.
Another one is where one gets it from both ends at the same time… one it the mouth that is.
There's also the 69 pose where the third is fucking one of the 69:ing girls.
All of these poses that I've suggested are intentionally adaptable for MMM as well… instead of poses which centers more around the female aspects of shemales… like double titty fuck for instance.