To remove An unwanted background-wallpaper image from showing up at windows startup :
Note : The backgrounds color is changed in the appearance tab. The wallpaper is changed under the background tab.
Right click desktop/choose properties/ the display dialogue box appears and you can find the background and appearance tabs here.
Make sure desktop background is set to none. Then hit the appearance tab and set the scheme to windows standard.
Restart the computer and it should be gone.