Right-Click on the desktop, not on a shortcut, select Properties.
Click the Desktop tab.
Look at the background image you see and the alternatives available, your picture might be the one selected.
Choose another background image, or none.
Click apply then Ok.
Thank you tigsounds - thanks to your suggestion, I have finally gotten rid of the unwanted pasted image on my desktop. Thanks also to nhasian! I appreciate your help very much!