The Command Line Interface (CLI), can be used to automatize tasks like converting images between file formats, resize them, or exporting sprite sheets. Some simple examples:
Resize your images with several scales:
aseprite.exe -b original.ase --scale 2 --save-as output-x2.png
aseprite.exe -b original.ase --scale 4 --save-as output-x4.png
aseprite.exe -b original.ase --scale 8 --save-as output-x8.png
Export only one layer:
aseprite.exe -b --layer "Foreground" sprite.ase --save-as foreground.gif
Export all layers as different animations (only on beta version):
aseprite.exe -b sprite.ase --save-as layers-{layer}.gif
More information and examples in Aseprite CLI documentation, and remember to check some platform-specific details or where to find Aseprite.exe.
Feel free to ask questions about the CLI here or share some examples about how you are using it.