I'll help you out 
Your rat needs to be exactly half as high on the southward facing sprite as it is wide on the eastward facing sprite. That's the classical perspective used in 90% of the oldschool RPGs, including the screenshot you showed.
It's basically a variation of isometric, but rotated 45° to have the four cardinal directions facing in up, down, left and right. This means that a barrel (which doesn't have corners), should look identical in isometric and this perspective.
I hope that helped.
It did, thanks a lot. There's a name for this perspective? Or it just called classical?
What about humans or antropomorphic creatures (which are very narrow)? Is there any guide/page, which I can learn more about this classical perspective?
This is what I've done so far (I know the head is too big compared to the body, but I like it

, maybe I should make de body a little bit bigger, or make the body even more frontal):

I still need to fix the side sprite.

But I jump to other part of the project or even to other stuff when I get a little stuck.
Thanks for the help
