Perhaps the image names could be dynamic (like rate1, rate2, rate3) based on the rating. I did this with the rating names too (like "accurate", "well sourced") to make it easy to add on to.
At the moment the images are integrated with css , so that you see the text if css is not enabled (screen readers etc.).
I am actually not that sure if replacing the spelled out version with icons helps that much - maybe have additional icons, or do something with color would be good. But thats really not my topic - my designer told me to better stay with black and white. But I could ask him, maybe he has an idea...
Cheers,
Joerg