Art Beyond Reality is a community for artists of the fantasy and science-fiction realms. All kinds of art within these genres are accepted including fanart and art with more adult themes, but please if you are posting something questionable use a special LJ cut tag or in the link to the picture and label it as such so that the members know what awaits them. You will of course have to have a place that you are already posting your art so you can link it to your journal. If you are looking for a place, you could try Elfwood, Side7, or Deviant Art.
It is open membership right now, but you will have to post something at least once a month or you will be banned. If you are just wanting to view the art, then it will be up to each individual artist as to if you can see their work or not as you will not be a member of the beyone_real community and will only be able to see unprotected entries.
Art Beyond Reality has two sister-communities. bookwyrmmes is a book club for lovers of the fantasy/sci-fi genres, and world_of_wonder is a community for writers of the same. Please feel free to look into these as well!