Wakfu isn't pixel art.

It mixes two different techniques :
• Probably vector art for characters. Allows easy and lightweight animation, beautiful
smooth curves and lines you can zoom in, but gradients are limited and you can't really
add textures. You have to learn how to use a vector software like Flash to create and animate
clean assets, but trust me (I have a huge background in Flash), obtaining good results is extremely
hard. Most of the time you'll get a really cheap vector look if you don't have 1-2 years experience
in vector art.
• The background is mostly made of simple tiles painted in Photoshop or another advanced
software. You need to have a solid art background to achieve this kind of rendering. There is
a lot of places to learn, like
http://psd.tutsplus.com/ or youtube.
So there is no magic here, you can't cheat time, experience and talent. You have to earn
them hardly if you want a result that clean, by spending a lot of time to try, compare,
understand, learn, observe, photograph…