The image filepath has to be relative to the current working directory. The working directory is possibly different to the directory of the python file.
The name and path of the file can be get by __file__. The current working directory can be get by os.getcwd().
If the image is in the same folder as the python file, then you cnb get the directory of the file and change the working directory by os.chdir(path):
import os
# get the directory of this file
sourceFileDir = os.path.dirname(os.path.abspath(__file__))
os.chdir(sourceFileDir )
or concatenate the image filename and the file path by os.path.join
. e.g.:
import pygame
import os
from Introduction import *
# get the directory of this file
sourceFileDir = os.path.dirname(os.path.abspath(__file__))
# [...]
GameBackround = pygame.image.load(os.path.join(sourceFileDir, 'backround.png'))