HTAccess: Cache Images

ExpiresActive On
ExpiresByType text/css "access plus 1 month"
ExpiresByType text/javascript "access plus 1 month"
ExpiresByType text/html "access plus 1 month"
ExpiresByType application/javascript "access plus 1 month"
ExpiresByType image/gif "access plus 1 month"
ExpiresByType image/jpeg "access plus 1 month"
ExpiresByType image/png "access plus 1 month"
ExpiresByType image/x-icon "access plus 1 month"

An overview about how to speed up your website you can test it at:
https://developers.google.com/speed/pagespeed/insights/
https://stackoverflow.com/a/35878101