Selling Art Help!

[Zombie Teapots]

So, I'm going to try to start selling my art, both for USD (commissions) and Gaia Gold (fun/practice), so I'd like to get an idea of what my art might go for.

I would probably offer:
headshot+lineart
headshot+lineart+color
full body+lineart
full body+lineart+color

Do you have any suggestions on how much I should charge -- either in gaia gold and/or in USD?

The "Featured" section of my Deviant Art will give you an idea of my style: http://tipping-teapots.deviantart.com/gallery/

Thank you so much for your time!
~Tea