The game is looking really cool already! I really like the art as well!
A few suggestions:
1. It can be hard to know when you win balls, maybe have balls travel through a seethrough tube before they get into the tray (could have a few bends so its fun to watch them enter the tray), also maybe have some lights around the board that flash in reaction to whats happening (would probably need a setting to turn the lights off as could affect people) could also add some sound effects or voice lines when you get the balls in the slots as well
2.It could be cool to be able to change the colour of your nails in the game. Could be unlocks and rewards in the full game as well
3. The coin slot is very cool and immersive! Some other ideas for imersion could be have the balls dropping counters be part of the machine as an led display or analouge display. Other on screen information could be part of the machine as well. Could also be nice to be able to see the edges of the machine and see the parlour at the sides of the machine to feel like you are in the parlour.
4. An idea for a new table is that parts of the table unlock when you get in certain slots, or the table could be split into parts and slots and tubes transport the balls to the other parts
Im really excited to see where this goes as the idea of a game of chance rpg is really cool, being able to play all of these games with out having to actualy gamble is cool!! There is also so many cool things you can do with the rpg elements, like all the games have collectibles, could have some characters you can talk to in the parlour(will be cool to see more of your character art!) with some story, secrets, character customisation and more!
Sorry for the wall of text, but I hope some of these suggestions are useful or interesting. Quick question what game engine did you use? Good luck with the development! :)