New info is going around that IMGUR is going to begin purging a lot of content from their platform. It's not entirely clear at the moment, but it seems like they intend to remove adult content starting the 15th of May. Here is a list of approved domains in my current subs:

Domain Whitelist

Imgur
ImgPile
ImgBox
PostImage
RedGifs

ImgPile is my personal favorite. It's a well-designed site, provided a thorough list of direct and embed URLs, and has been snappy fast when I've used it.

Feel free to suggest other image hosting services in the comments and I'll look into them.