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Here is a Nexus 7 lying flat on a brown, wooden table top at an extreme left angle. To the bottom right of this image are a white and chrome stylus and a cup of black coffee. A few coffee beans lay next to the cup. In the upper portion of this image is a folded newspaper or notebook, grey with white trim. A heavy, stone lamp base sits above the Nexus. The stage on the Nexus will display your product screenshot nicely at a portrait 800 x 1280 px.
Drag & drop not supported, but you can still upload via this input field: