I have gotten help from FSF licensing and they suggest using the GPLv3 to license the art as well as the code.
After asking this question:
i'm a volunteer for a non-profit organization and am helping them
develop a free open source Android app that i hope will be licensed
under GPLv3
We are going to use the logo and some other graphics files from the
organization and are wanting to use licensing of this artistic work to
protect ourselves from anyone doing damage to the reputation of the
organization
What license would you suggest us using for our artistic work and also
the code itself? (Any thoughts more in general about what we can do to
protect the organization?)
I got this response back:
GPLv3 is an excellent choice here for both the code and the art. Section
7 of GPLv3 permits that your organization place additional terms which
will help protect the work:
Section 7.b allows your organization to add terms "... Requiring
preservation of specified reasonable legal notices or author
attributions in that material or in the Appropriate Legal Notices
displayed by works containing it ..."
Section 7.c allows your organization to add terms "... Prohibiting
misrepresentation of the origin of that material, or requiring that
modified versions of such material be marked in reasonable ways as
different from the original version ..."
Section 7.d allows your organization to add terms "... Limiting the use
for publicity purposes of names of licensors or authors of the material
..."
And section 7.e allows your organization to add terms "... Declining to
grant rights under trademark law for use of some trade names,
trademarks, or service marks ..."
I hope this is of help. Please feel free to write back with further
questions.
I'm grateful for the service that they provide at the FSF (Free Software Foundation) and i hope me posting this help someone else too