Hi lvcard,
Thank you for reaching Microsoft Community.
I would like to confirm first on the concern, do you mean the screen saver which shows whenever the device is left idle or is it the wallpaper which serves as the background image of the desktop screen?
Regarding on the sage green image that you got when you first got the device, was it the same image with the blue colored image you are getting right now but just in sage green color or was it a different image also?
Kindly try to open the File Explorer then navigate to this location C: > Windows > Web. Try to check on each folder listed if the sage green image that you are looking for is there.
Kind regards,
Marrion