Sure, I've played quite a few idle games in the past. I can give some ideas, but this is just from the top of my head. Thanks for replying by the way, I'm always glad to give feedback for a game that deserves it. Anyway, here's what I can think of now;
Most idle games become more engaging as you can see your progress manifest physically, showing how far you've come. Cookie clicker does this with its milk system, and others might make some slight aesthetic changes. In this game, I think slight visual changes would be the way to go, and what I mean by slight visual changes could be something like the background changing in colour, the tentacles unlocking more textures as they get used (suction cups, warts, etc.), or very expensive items in the game that take a lot of time to get. The most expensive thing is for 5000 points, but you have a counter for like a hundred thousand. Might as well use it.
One other thing is achievements, stuff like clicking the breasts 500 times, making the girl cum 10 times. You know, basic stuff like that. It might not be a direct upgrade for gameplay, but it is something for the player to do. Of course, it's always better when achievements are rewarded, like how the breast achievement could unlock new piercings, or something else minor. It's always great when there's something else you can do aside from the idle content, something else to focus on, and achievements is a great way to do it, and it doesn't affect gameplay that much.
One other thing is that many idle games have an "active" option in progression. With cookie clicker it's the golden cookie and pairing that with the grimoire for crazy combos. You have something similar here with the egg system, and I could see that getting explored further. If you add more items with more cost, then there's greater incentive to try to get more points some other way than just waiting. But yes, the prices would need to be really high.
Also depending on the size of this game, I wouldn't mind more repeatable upgrades. Everything you can buy in this game has an unlockable customisation that comes with it, but there can be upgrades just for the sake of being upgrades, and not just customisation. The gropers for example are great, but since each one you add gets added to the scene, there's a limit to how many you can get. But if you had some ambiguous upgrades like "slimier tentacles" where each new upgrade gave 1% more point accumulation, you could keep buying that upgrade without having to worry about making anything out of it. Again, it's just something else to do, but at the current scope of this game I don't know if this specifically is needed. Just something you could consider adding, if you want to add more stuff.
I've rambled long enough now. The gist is this; More stuff to buy for a higher price to incentivise grind, alternative gameplay options to variate the gameplay loop, achievements for items you can't buy, and radiant upgrades that don't have visual changes for more stuff to buy.
That said, one of the core things about this game is customisation. You could just add more poses, more clothing options, even a colour wheel for the tentacle colour, and that would add a lot to the game. There's really no need to improve the gameplay as it is currently, because there's just not a lot to buy. It took me just 30 minutes to buy out the shop in its entirety. Which is to say, there's currently no need to change up the gameplay, but when there is, hopefully you were able to glean something from that wall of text.
I could give some ideas on some customisation options if you're interested on my opinions on them, but I feel like you have enough on your plate there as it is. Also, feel free to contact me on discord (wibiz9000) if you want my opinions directly, without needing to wade through walls of text. Regardless,
Thanks for reading all of that.
