You can store your downloads in your account when you signup!
This photo features a young lady working on her Macbook pro while sitting on her bed at home. In the scene, we also have her friend so this is a great mockup template for any kind of social app. She has the Macbook pro on her lap and using the track pad to use the computer. The setting is fairly casual but could also fit for doing homework.
Drag & drop not supported, but you can still upload via this input field: