I really enjoy this game, and I have played it devotedly for quite some time!
Here are some improvements that could spice up this game I could suggest.
Right now, nothing happens when cats have a low hunger/thirst/anything bar. If I forget to feed them, nothing really happens except for the fact that they all rush for the food bowls when I refill them. However, I think there should be side effects- a cat might become tired and lethargic, for example- but please don't kill off any cats! x( Also, if this suggestion is brought to life, there should be a message indicating the effect.
Another suggestion is a table and table items. Right now aside from lamps, toys, rugs and a sofa, our spaces kinda seem empty. If you added a table and a table item, the cats could sleep on the table (or not). The items would make it look more fun, but they aren't necessary. Also, I think it would be nice to have a cat tower- it's a classic.
One more suggestion- the game is beautiful, but I think the tone could be a bit more interactive! Night could just be a darkened version of its current state- but cats could just have simple glowing eyes, ooo! It could rotate from night and day every, say, fifteen minutes? And occasionally a short storm would affect the yard, maybe some puddles would spawn and then vanish.
Anyway, I understand if these seem too complex! If any of these are taken into consideration, I would be honored.