What is ArtStation?
ArtStation is the industry hub, where media & entertainment artists can keep up with each other and find new inspiration every day.
Comments and Reviews
Said about ArtStation as an alternative
It has a professional air while allowing artists to upload multiple pictures into one post, much like Pixiv does. However, the professional vibe isn't everyone's cup of tea, but it makes for a fantastic art portfolio.
Better art quality, better artists and a well moderated community.
ArtStation overall is the best alternative to any site I've seen, it also encourages better work, even if considered more on the commercial side, you still can upload there, and it does good for your projects too. Otherwise, keep it to yourself.