1. There's Nebby cats spread out all over the map. Find them and unlock scenes with Nebby.
2. Frisk has self-pleasure scenes now. Three to be exact.
3. They added a new background for one of Chara's skin, IIRC. Though I didn't check that out yet, so I'm unsure.
4. There's voice acting now. Although none for the sex scenes yet, I think.