Hehe, I have to admit that just the other day I thought of creating a map similar to this one, with the starting positions in that order.
It looks good and you must have worked on it alot, but unfortunately there are some balance issues, and you might want to consider fixing it up.
The map is just too tank-friendly, meaning that nearly every expo and every main can be hit by siege tanks. Also, the paths that lead to red and purple can be sieged very easily by the other players, they just have to place a few tanks on the cliffs and gg.
There aren't that many paths to move from one place to another, especially when you want to move from the top area to the bottom. The map could use some more room for troops to move with ease.
And probably too many geysers, you could have main and nat expo with gas, and a mineral only for each player.
I would definately fix up this map so Terran and their pain-in-the-ass siege tanks
wouldn't have such an easy time. Mains shouldn't be so easy to siege. Good effort though, it's nice to see others making 6-player maps. I know how hard it is to make a map for 3v3, especially on 128x128 size (all 3v3's should be made on this size). I've made around 20 3v3 maps, so if you want I could give you some tips and help you with this one.