Astia automatically resizes images to make them look nice depending on their location in templates.
Minimum recommended image width is 1920px.
Please try to select images that match the minimal width to avoid whitespace, bad alignment and other image related problems.
Regenerating Thumbnails
If you install Astia on the existing blog with existing images we strictly recommend that you should regenerate your images.
Please install and run Regenerate Thumbnail plugin: