But I suggest as a first excercise to take one single image (I'd take "autumn colours, perugia 1") and do 2-3 further versions with the same size but decreasing compression, and post them in a comment -- for us to comment :-) (We frontpagers can delete it later.) *Lunatic*, n. One whose delusions are out of fashion.
Save as JPG.
Flickr shouldn't do too much damage after that.