I don't mind at all releasing whatever graphic I have done for Bitcoin in the public domain, it's just that I have no idea in which license is the original logo done by Satoshi, especially the symbol. Is that symbol in public domain? I know this may sounds dumb, but it has to be, right? If it is part of an open source project. I am no lawyer or programmer familiar with this sort of things, I am just a bum for god sake. So perhaps someone can enlighten us.
It's released under the MIT license. CC-A would be most appropriate for your logos, I think. They could then even be included with Bitcoin without any trouble.