in this theme you can customize the background with your image.
Banner filters to edit the image / Opacity / Background color

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Cover
The background image fits the screen
Top image fits to layout

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Cover + Alpa Channel
Set opacity with Slider

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Tile
the background image is tiled
keeping original size

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Tile+ Alpa Channel
Set opacity with Slider

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CSS filters with Slider
Body background image
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Brightness
Contrast
Saturate
Invert
Grayscale
Sepia
Opacity
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+ CSS filter
This further effect is available with fixed value

BLUR