CssSpriteGenerator (nuget): Reduce bandwidth costs and page load times by compressing large images on the fly, physically resizing thumbnails and combining small images into CSS sprites to cut down on request/response overhead. No need to change your site, just add this dll and add configuration to your web.config. Extensive documentation.
Keywords: Performance|ASP.NET|CSS|Sprites|Image|Compression|Resizing|Thumbnails|Background|Images