Do you have permission to post this? At the very least you have to credit the source of this image (game+company), but even that doesn't make it magically alright to post this without written permission from the company that owns this artwork.
That's better than nothing. However, if you want to post pretty art, then learn to make pretty art. This is art theft, and it doesn't make you a better artist. It takes a lot of work to get to this skill level, but it's very rewarding when you do!