I was reading Can a company trademark a public domain name like "Arkham"? not sure if this is the same.
I'm working as volunteer at OpenClipart.org, site that provide Public Domain vector images (it use Creative Commons Zero license).
I was asked multiple times if someone can use our clipart as logo. I always answer that he should modify the clipart because someone else may use the same clipart for his logo. But what about trademarks? Can Public Domain image be used as is for a logo? Or should it be derived artwork?
What should I answer to person that ask about using PD (CC0) clipart as logo or if he can trademark it?