Mimiroppu:
I usually follow the artist's range of pricing unless it's absolutely ridiculous. However, I suppose I can add my two cents!
That chibi is too adorable! I'd go for 500 to 1k gold for it, since it's so detailed, and colored always adds a couple hundred. I'd go for 300 for lined images.
The full bodies are amazing! No doubt 3000 gold would be more than acceptable. Since it takes more time to ink them, I'd add 1000, and for every extra person in the non-chibi images, I'd price it for 500 to 1k.
If you think about backgrounds, depending on the amount of work that goes into it considering detail and color, it'd probably be acceptable for a grayscale background to be around 500, and a colored one to be 1500.
These, however, are my ideas! I've never owned a store, and I'm just going on what I've seen.
However, if you want to make 6k, throw a PM my way! The full-bodies are astounding, some of the best I've seen around Mene.