Actually I don't know why the icons have to be anonymous. As you point out the fanfics aren't. (Also I don't do icons so I don't eeven insights in the communities who share icons)

I also try to fairly judge artworks. I can recognize some authors - ahem - from their style and I like that: it means that every author has some kind of signature and that art isn't anonymous at all. But I try to be fair because I know what it means to create a fanwork, you spend time and try to do your best and it's something that you do for free and pleasure, sure, but that doesn't not diminish the quality. So every ficwriter/fanartist etc. should be rewarded when their work is good. If you enjoy the art than tell that to the artist, that's my philosophy.