On one hand, that's mostly referring to generic girls and they are slowly getting basic set of sex renders. Right now Av136, the white haired elfin girl, won the poll to have renders. Before that it was Av126. Before that Av170, Av134, Av113, etc. On the other hand, with regards to scripted slaves, some girls seem to be more favored than others which can lead to some girls feeling left behind since there's only one developer for this game. There is a couple of people on the discord assisting with the new combat backgrounds for example, or creating faction-themed random male NPCs and a couple of female NPCs via image editing. There is one person that creates new fully rendered female NPCs (Av179 and Av180) as a fan project that did get added to the game. But those are passion projects.
As for quests, they are old quests by old characters slowly being resolved. Aria, Averil, the conclusion of prowlers, and the ability to add Tori to your house. The "new one" is Seve, and even she is a subscriber tier requests from way back according to one of the progress posts.
