To apply the same visual to all your scenes, go to Visuals > Select the image > Click on Apply Visual to all. You can use the Visuals available at the Library

To use your Textures available on Pictory, go to Visuals >Textures > Select from the Background textures or Solid colors > Apply visual to all
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To use your own visual, go to Visuals > My uploads > Browse image from your computer > Select the image > Apply visual to all. You can also use the images saved under your Recent and Favorites

Please note that panning of the image is turned off when the Apply to all option is selected.