This site is an archive for actual posters for actual events. It is a historical record. Imagine going to a newspaper museum and some of the articles were fan-art(icles). You begin to doubt the legitimacy of others if you don't know which are real and which aren't.
In addition, just because you don't use a trademarked or copyrighted logo does not mean it's ok. Selling a poster based on a bands name is not cool if you don't have their permission. And saying you don't plan to sell them...unless someone contacts you? You plan to sell them. You just don't have the confidence to put it out there for sale. Get a classified, but make sure they know it's not a legit gigposter before they buy it.