"Imgur is doing a purge. Effective May 15, the site will scrub pornographic images, along with other inactive content that is not linked to an account, from its archive. The popular image, GIF, and meme service is encouraging people to save images if they don't want them to vanish from the web forever." - Wired.com
If you have pictures that you use for your characters that are nsfw or "racy", it's advised to pull them from the site. There are other sites that will allow the pictures; mostly if they are selected as 'private' in the made albums.
I myself have moved pics to Photobucket.
Here's to hoping you find a good site that works for you.
~V~
EDIT: Moved to lensdump.com (as of June)...that seems to be holding up well.