Nice add, Hamza!
You can apply SLDS classes to the MAIN BOX of this Screen Component.
The major classes for themes are:
slds-box slds-theme_shade slds-theme_alert-texture
More Details: https://www.lightningdesignsystem.com/utilities/themes/
To use this, set the input attribute
The default values is “slds-box slds-theme_default”
But not limited to these classes but you can also add other classes like padding, margin, grid, alignment, visibility, and custom CSS classes as well (especially if you’re using this screen component in Lightning Flow within a community)