Wiwa

Hi, I am experiencing a problem regarding cover art on my NWZ-X1050. I've added covert art to all of my songs, but all covers look unsharp (it looks blurred, because the resolution isn't right, I guess) on my NWZ-X1050. Nearly all images are 500x500, which seems pretty standard to me. Is there any way to solve this problem? If not, I'd rather not have any cover art at all than very blurry cover art. Thanks in advance!