Yes, you can. You can either set to use an image pattern that’ll be applied on all your pages by using the Background Pattern Upload option under the Morphis Theme Options > Skins, Styles & Fonts panel:

The Background Patter Upload option under the Theme Options page


Or you can set a full background image/pattern on a specific page by going in to your “Add New/Edit” Page of your particular page and uploading your image in the Full Background Image upload option:

The Full Background Image upload option under the Page-Level Settings