Pornography
Pornography, X-rated movies, home porn, hard-core material that depict graphic sexual acts, and amateur porn are not permitted. Unrated erotic videos and DVDs of the type you'd find at a typical bookstore are permitted for DVD distribution. Any permitted nudity, graphic titles, and descriptions must be sufficiently concealed with censor strips on all items containing such content.
From their content guidelines..? Does this only apply to video porn, or what?
Also I found this:
Public Domain and Other Non-Exclusive Content
Some types of content, such as public domain content, may be free to use by anyone, or may be licensed for use by more than one party. We will not accept content that is freely available on the web unless you are the copyright owner of that content. For example, if you received your content from a source that allows you and others to re-distribute it, and the content is freely available on the web, we will not accept it for sale through CreateSpace. We do accept public domain content, however we may request that you provide proof that your submitted material is actually in the public domain and may choose to not sell a public domain title if its content is undifferentiated or barely differentiated from one or more books already available through our service or available through other retail sites.
Sooo... Font, digital brushes, all that jazz... stuff that's free to use for commercial content. Are they gonna make a big fuss with me about it?