Chances are your images are named something like "X20110105%homepage%product%1" - you can double check this by right clicking on the image and choosing properties. The problem with names like these is they give no indication to search engines about what the image is actually of. Instead, change the name to include key words e.g. if the picture is of a MacBook Pro, change the name to apple_macbook_pro_white. This way search engines will have more indication as to what is on the page and will therefore rank your page higher.