I feel like I shouldn't add ideas because I haven't done any of the practices yet, or asked for the password to the erotica SYW forum.

*Is a lazy butt.*
However if you want ideas anyway, I've got plenty. My first thought is that the practices have focused on a specific sex scene, I'd like to see a practice which is about erotic worldbuilding (invent a sexual cult or holiday, unusual alien or magical creature sexual biology, a future fetish, etc). Also one where one character fantasizing about another while some non-erotic action is going on (Could be playing secret admirer to the object of desire, getting yelled at by the object of desire, being study/work partners with them, cleaning alone, or watching the object of desire with another lover.) Oh wait, was fantasizing already done???
For more simple ideas, I'd like to see incest (has been a big topic in the Sandbox recently), invent a new sex toy, transformation (I'm thinking magical bod mod but could be a gender change, turning into a superhero or werecreature, non-magical bod-mod, forced feminization (actually I've never seen a forced masculinization story, do they exist?), feeding/inflation/other growth/shrinkage, or any kind of training to transform someone's mannerisms, style, or personality. Cuckolding would also be an interesting challenge because that's one I don't really understand - I'd probably do it badly but it would be an interesting learning experience.