You can put disclaimers in your post like "Not for commercial use" but that really doesn't deter anyone. Ultimately, anyone can save the image of the map to their hard drive and put it up in some out of the way place that only a few know about and take all the credit for it and you may never even know about it. I'm betting that sort of thing happens all the time (cuz we've seen it many times before here) - dude sees a cool map, saves it, shows his friends, and tells them that he made it. However, the jig is up when they ask him to make a map for them the same way and he can't so they begin to doubt the first map was his. The dude may come back here and put up a request for a map that matches your style and that should raise red flags about his intentions. Most of us here keep what we call "Inspiration Folders" where we save cool stuff or neat ideas to explore in the future - whether it be a technique for hills or forests, cool continent shapes, neat tricks, etc. and we sometimes explore these things later in our own work. Nearly all of us give credit where it is due saying something like "I saw a neat thing by Mr X and here's my take on it". If your map goes into a published book and someone comes along and says "Hey, you stole that map from my friend cuz I've seen it before" you will certainly not have to deal with any legal questions as the dude who lifted your map knows that he did so and would never call you out on it...just his unknowing friends would. So those folks you can just ignore. Should your map just linger on a shelf somewhere for the rest of your life then there's no harm. Should you see your map appear in someone else's book then you can call them out on it and you might actually win the case but you'd lose a lot of money to the lawyers. Should the book sell millions of copies you might be able to get some royalties out of it whether you sue him or agree to something out of court. So, in the end, if you post it you should just assume that the world has seen it and someone somewhere has a copy saved...it's the way of the world. You always have your originals and the courts can settle things if push comes to shove. Not much of a confidence booster but I'm a cynic about trusting other people.