I have drawn a grass sprites as a background, my question is what should I add to my game.

Start with moving parts, such as a player character and NPCs. Getting a game loop going will more organically tell you what else is needed.

I have drawn a castle on the screen, next I am going to draw a character and have it move with the keyboard.

Now all you need to do is figure out what kind of game you want to make, and figure out the details of the design yourself.

Tom Sloper said:
Now all you need to do is figure out what kind of game you want to make, and figure out the details of the design yourself.

That's not how AAA studios work. My GAWD, you of all people…..

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