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If your design is meant to be seen outdoors, how about this bus stop mockup? You can drop any 800×1200 px screenshot to showcase your ad on a real life bus stop ad. The photograph was taken on a nice suburban street with loads of trees. A white car drives by, about to pass this ad mockup.
Guy Standing in Front of a Wooden Wall Holding a Poster Mockup a10321
Drag & drop not supported, but you can still upload via this input field: