Trades with Luxidoor doesn't make sense. Polytopia starts with no tribes knowing any other. Vengir has a story brhind this, but that means NOTHING, it doesn't mean that there should be a another tribe with a thing nor story behind.
Use any art program that has the tool "polygonal lasso" I use photoshop, if you can't afford it gimp or inkscape works well from what I have seen, ask PolytopiaFanGirlXD (creator of bogbog tribe.) for more tips. If you want to simply change the color of grass for a specific grass color you can google search for an image of a polytopia field and change the hue and saturation of the whole thing to get different colored grass. Same applies to any other templates you use, but to make custom shaped mountains and stuff like that it wil take a while.