there are two optimizations:
- optimize with a plugin, or by hand + SAVE FOR WEB option (PS or GIMP) or other online or local image manipulation program, or use CDN
- add to .htaccess the lines : ExpiresByType text/css "now plus 1 week" ExpiresByType application/javascript "now plus 1 week" ExpiresByType application/x-javascript "now plus 1 week" # Image files expiration: 1 month after request ExpiresByType image/bmp "now plus 1 month" ExpiresByType image/gif "now plus 1 month" ExpiresByType image/jpeg "now plus 1 month" ExpiresByType image/jp2 "now plus 1 month" ExpiresByType image/pipeg "now plus 1 month" ExpiresByType image/png "now plus 1 month" ExpiresByType image/svg+xml "now plus 1 month" ExpiresByType image/tiff "now plus 1 month" ExpiresByType image/vnd.microsoft.icon "now plus 1 month" ExpiresByType image/x-icon "now plus 1 month" ExpiresByType image/ico "now plus 1 month" ExpiresByType image/icon " in order to make the browser of the client to rember the image for one month
The result is speed, your site is going to be loaded very fast so it is going to be high in Google ranking