It's you, matt30, who are principally at risk. By making your icons available under a Creative Commons license from you, you are claiming rights over someone else's intellectual property: the right to determine how their trade marks can be used. If they find out about it, they will have little choice but to come after you, because undefended intellectual property rights can lapse. What's more, anyone else they pursue, who claims that they were misled by you into thinking that they had rights from you to use these icons, could drop you right in it.