from tkinter import Tk, Label, Button, PhotoImage

win = Tk()
win.title("Кнопка на картинке по центру")
background_image = PhotoImage(file='WonderField.png')
background = Label(image=background_image)
background.pack(fill="both", expand="YES")

btn=Button(win, text="Hello World")
btn.place(in_=background, relx=.5, rely=.5, anchor="c")

win.mainloop()

from tkinter import Tk, Label, Button
from PIL import Image, ImageTk

win = Tk()
win.title("Кнопка на картинке по центру")
img = Image.open('WonderField.png')
background_image = ImageTk.PhotoImage(img)
background = Label(image=background_image)
background.pack(fill="both", expand="YES")

btn=Button(win, text="Hello World")
btn.place(in_=background, relx=.5, rely=.5, anchor="c")

win.mainloop()