I think the question is structured as lends itself to two interpretations, one using a picture as a background, as the photo stand which asks the question and the other using a 2D drawing to a 3D model from this. I will explain how a drawing is used as background.
Is very easy, only you need a file with picture or drawing in format JPG.
With the model open in solidworks you must go to:"Scene, Lights and Cameras", display the bottom "Scenes" then double click in "Background", this open a new dialogue "Edit Scene", then in Background Click in the bottom "Browse" and select the picture or drawing that you want and surprise the picture or drawing is in background of your model.
Enjoy it. "LIKE" and "It worked" are welcome.
Answered with a tutorial: https://grabcad.com/tutorials/how-to-model-a-3d-part-with-2d-drawing-background
Another solution is to use the background option. This option was created specifically to answer your question. In SolidWorks access your 'Options' <Tools - Options> then go to the setting 'COLORS'. In the middle you will see 'Background appearance', from there you can select Image file and use one of the many standard image file types to set as the background image in your design window.