I have a huge folder of boxm@s transparent images if you need them.
For the anime though you may have to photoshop them yourselves. I recommend using Photoshop's polygonal selection tool to carefully go around the edges of the image, and then carefully erase the rest you don't want.
IMO, you don't have to go super clean because it won't be terribly noticeable if you have a small mistake on a business card. Just do whatever you think looks best! Happy editing!