Hi,
it might be nice to use libjpeg-turbo for SDL_image if it’s available:
http://sourceforge.net/projects/libjpeg-turbo/
http://libjpeg-turbo.virtualgl.org/About/Performance
It’s already happening in Fedora 14.
http://fedoraproject.org/wiki/Features/libjpeg-turbo
cheers,