Architect Pro comes pre-loaded with default images that are used as the backgrounds for the Front Page 3 and Front Page 5 widget areas. You may use this default image or go to
Appearance → Customize → Front Page Images to upload your own.
The default image size is 1920 x 1080 pixels. There are 5 Widget Areas on the front page. They range from front-page-1 to front-page-5. The demo content for these widget areas comes included with the theme.