This is really pretty. I love the simplicity and yet you have a good amount of detail in all the right places. Night work and loving the shading on the tail and shape of the fur around the ears and neck.
You use chat poses on graphical chat sites such as Wolfhome or Lupinar. Though their use isn't restricted to just chat poses, but can be a graphic for other stuff too. Journal headers, Tumblr image headers ect are also ideas.
A chat pose is an image of your character/full body/no background or very simple bg.