Shading advice

[Wikiwow]

I'm making these sprites of Macho Grubba from Paper Mario 2. I've only made two poses at this point, and I don't want to continue until I've decided non how to shade them. I do want them to resemble the Paper Mario-style, so I'm not sure if I should keep the outline black or not.

Here they are:

Also, if there's anything else you see wrong with them, go ahead and say so.