- I'm not really familiar with using anime pictures; the best advice I have is to pick an anime face claim and use official art of them. Using fan made art is theft and not allowed. Anime is art, so it's harder to find images to use.
As for the second question, unless the work is licensed under a Creative Commons license it's not free to use. Art is copyrighted without the artist having to do anything; unless they say you can use it it's almost a sure thing that you can't. Giving credit doesn't change the fact that you don't have permission in the first place.