Hello! I post 99.99% all things hetalia-related here. I have a step-by-step guide on how to ask pixiv artists permission to post their art on tumblr over there just below the tag page. I'm in the process of going through my 15,000+ posts to delete any art I've posted without the artist's permission, so please bare with me. And if you see any of the pixiv art I've posted that doesn't have the 'permission given by the artist' caption, please do not reblog it. Thanks and have a wonderful hetalia life!
(psst~I also track the hetalianforever tag)