It would be great to be able to unlock different skins for all of the Utility/NPC decorations, especially the Summoning Brazier and Teleportation Shrine. Would be amazing to have a variant for each god/realm, plus seasonal ones.
It seems like almost every creature now has new artwork from the old games (I think the slimes and pudding are still the same?), it would also be great if we could unlock all of their old sprites as skins. I prefer the new ones, myself, but that would be a ton more unlocks that would require the most minimal effort for Zack.
Finally, it would be neat to have another project that adds a new Utility decoration, the Mirror of the Inner Beast. This mirror would be used to re-skin the player to any creature they have S-rank knowledge of, or it can take a whole new set of randomly found scrolls to give us more unlocks to find (the latter sounds more fun to me).
Apologies if these ideas are already in the game.