We have a Tumblr Group that is linked to our DeviantArt RSS Feed. This allows the contents of our FEATURED section to appear on Tumblr. hypnotizedguys.tumblr.com
Don't worry Artists, your actual content is not physcially posted on tumblr, it never leaves DeviantArt. Instead a link is provided for your images hosted on deviantArt and a link for people on tumblr to click on to take you to *your* page on DeviantArt (not the group)
It is hoped this will increase the numbers who see your work, whilst ending the terrible practice some people do of copying work off deviantart and reposting, so the originating artist gets no credit and can no longer control access to their own work.
Mature/Adult material can only be seen on tumblr if the user is logged on Deviantart - so don't worry about underaged seeing it. Should you delete your material on DeviantArt it will not be visibile on Tumblr.
Subfolders won't be mirrored, so if you don't want your material on Tumblr, just post to a subfolder, not to 'featured'.