the navigation buttons on the front page are all individual. Change to all the same button and add in the text on top. That way you are only loading one button that is repeated, and the table takes care of the text which loads fast anyways. Also try to reduce the size of the quality of the button and it will load faster
Yes,
although not a big deal it will speed it up somewhat. The images also get stored better so the next upload is faster as well. Seeing as this loads on every page it will make a difference.
Another difference is the fact that you will reduce bandwidth traffic on your server location. So less costly for you.