It's a really nice pinball.
Especially the pixel art. Graphically speaking, you make a great job! The only things that could be improve in my opinion are the wheat texture and the ball which can roll.
On the other hand, you can improve the sound. The game is often silent. However the existing ones are really good. The most missing sound is the slingshots' one.
Gameplay wise, nothing mush too say apart from the chicken that could be turn off when the ball pass trough (not sure of this one).
Finally, in term of UI, it feels frustrating that the score go away when you finish the game. And configurable controls would be neat.
That's it for me. I hope these feedbacks would help you improving the game. As it is this pinball is already really good. I made some game already and I think I will play again in the future. Especially, if you make some updates as you mentioned in other comments.
Edit: I forgot to mention that it could be cool if you integrate tablet/phone controls as your game is playable on the web.
Also, it seems that when I got all the elements to increase the multiplier, the x2 light doesn't turn on. Not sure if it's a bug.