Plugin architecture is rolling in trunk!

Simple example on how to use it to use it:

THUMBNAIL_PROCESSORS = (
    'sorl.thumbnail.processors.colorspace',
    'sorl.thumbnail.processors.autocrop',
    'sorl.thumbnail.processors.scale_and_crop',
    'sorl.thumbnail.processors.filters',
    'your.own.processor',
)

read the docs to find out more.