What I've noticed so far:
- You need mushroom and fish for some dishes
- There are more crops than displayed in the direct
- HHP houses can have multiple floors
- Brewster has photos of the previous Roost locations in the cafe
- There is a DIY icon in the Roost (unsure of the implications)
- There are villagers in diving suits, sitting on inner tubes out in the ocean. (might be a stretch but it makes me hopeful for interactive furniture, but likely just a coded behavior for that area of the game in HHP)
- New plants on the Kapp'n islands, including plumeria bushes!!
- Isabelle's wearing a new outfit during morning aerobics
- There might be a new furniture series called stonework
- Old items have also returned, like the sushi platter, flower planter, Rococo, Ranch and Sleek series
- A new K.K. genre, Vocaloid (based off Miku)
- Eating cooked items gives you energy
- Fences of the same type but different color will not join (ex. natural wood and white picket fences won't connect)
- Smoothies are craftable
- There is a new DIY category for tools and kitchen implements (previously was just tools)
- New series of Nook Terminal items starting with"Plaza". Ex. Plaza Teacup Ride, Plaza Clock, Plaza Balloon Wagon etc. (It's interesting that they would put a new teacup ride in the game, when we already have a Nook Terminal exclusive one)
- There are multiple types of music boxes!
- There's a weed/vine themed ladder set-up kit
- The new villager Roswell has crop circles all over his body
He's a UFO enthusiast
- Amongst the mountains of new furniture/items, there is also a ring light (which I found pretty amusing) and large outdoor items like a bonsai tree and Torii gate (not seen in the Nook Terminal)
- Partition wall pattern is determined by what wallpaper is currently displayed (or the wall you're currently customizing)
- Pillars are customizable
- There is at least one new floor-to-ceiling furniture item (a wooden slat wall with a shelf)
- There are wooden sticks/branches coming out of the water on Lottie's island (???)
- Shino's HHP house request is "A Stage to Jam for Japan", this makes me think she might be a peppy or snooty villager (but doesn't really mean anything for certain)
- Isabelle's eating a chocolate ice cream bar at home... Isabelle WHYYYY?!?!??
Will add more if they come to mind