Split background image and pack them as CSS sprite

[coolwanglu]

For raster images only.
A good algorithm: http://www.codeproject.com/Articles/210979/Fast-optimizing-rectangle-packing-algorithm-for-bu

Another algorithm: https://github.com/yostudios/Spritemapper

[X4]

Good idea, but this only makes only sense for packing small images. Therefore you need a 2nd compilation phase, which packs all images with a dimension less than 10% of the source canvas into one mega-sprite.

It means that only on PDFs with many small images you will have a noticeable impact on file-size and load-time.