Hello, Crissi HiME! Thank you for making sure to clarify this.
Art traced from pre-existing artwork cannot be sold in the Art Shops. Edited bases (from a separate base maker) are also not allowed unless permission is given by the base maker, and even then it is highly discouraged because permissions can be difficult to work with if the base maker changes their mind or if one of the involved individuals abuses the agreement.
Referencing images is acceptable, but even images from Google that aren't as clearly owned as artwork may have some copyrights to them, so we highly discourage tracing unless the artist is definitively using a free-use source or their own images.
Ultimately, the tracing of images that are copyrighted can and will be considered art theft.
If you're not sure if the piece of art is considered art theft, you can always report it (through the Report button) or PM one of the moderators: there's no consequence for putting in a report, even if the artwork doesn't turn out to be stolen. n__n We appreciate the concern and the effort.