So, firstly, great game, way better than I anticipated at first glance, I have to say that the vibrant pink for your main page hurts my eyes a bit, wouldn't hurt to put a darker color, (or to give your page a better design), but I digress already.
My suggestions (in no specific order) :
More diversity in poses dialogues, be it futa or non-futa, right now it's too repetitive.
Different VFX for each character.
Random events on world map. There could be a random chance each day that some case has an event on it, signaled with a small pixel art representing what it is. I think it would be a great addition for many reasons, you could put minigames in them, you could put scenes and dialogues with characters (not necessarily H-scenes btw), and it could be way to get some stats with the girls, by interacting with them during those events.
Of course, because I'm not an asshole, I will also some ideas:
Beach party, a gathering of monsters girls on the beach, there's drinks, music, dance, and perhaps some minigame to gain some items and impress the girls (or not), and the beach party concludes with... fireworks? I don't if that exists in your world, but understand what I mean.
Of such events would mean you'd have to create art for the background and characters and all, and make the event vary depending on who accompanies you, (who you dance or drink with, who you try to impress with the mini-game.) So it would definitively take much work, but hey, I think it's cool.
There could be some hunting events with Silvia or Lya. Some sea events with Talia, (fishing, swimming, breeding...)
I know it'd take some work, but I think it would be great content for the game.
I liked the way we got Silvia and Oriana, would be nice to integrate that with other characters, like Lia, I feel like she wouldn't go down without a combat, or just try to prove superiority over you. And, expanding on that, could be nice that recruit some characters via some events or story-line, like Kinwa. She's always talking about her mistress, so maybe she can't join us on our great... Adventure? Anyway, maybe we would have to battle the mistress and defeat in order to recruit Kinwa? Just an idea, but I think it would open a whole new story-driven aspect of the game.
Like everyone else, I want new characters, it's not like we're very limited by our concept anyway. For some ideas: a bat-girl? A bee-girl? (Which could mean we would have to recruit by talking with the bee-queen since she's just a worker, and thus can't leave the hive.) Maybe a rat-girl? A cow-girl ? The ideas just keep flowing. But with so many characters, we'd have to think about our caravane space. As of now, I find the movement within the caravane with the mouse to a bit clunky, but perhaps it's just me.
I think that's enough for now. Thank you for coming to my TedxTalk, and sorry.
Of course, you're free to ignore all my suggestions, but I genuinely tried to recommend things everybody would want, and not going too much into my own personal desires.
Anyway, like your game, waiting for the updates, take care, and thank you.