Looks awesome for a rts! 
Thanks
My idea was to make an RPG without spliting the map into sections. I just wanted a big map that you could explore without interruptions. But this is just a map editor, so on paper the map may be useful for anything from an RPG to an RTS to a top down shooter or whatever.
I love how your tiles merge seamlessly and you can vary the height.
For the tiles merging between types I used a very, very dirty trick. Instead of making special tiles for combinations (that would have been a nightmare), I did this for every single tile:
So, when two different types of tile are next to each other, they "blend". It doesn't look as good as making especial tiles containing the combination, but it saves A LOT of work.
And about the height and elevations... arggg, screw them. They are incredibly frustrating, but at least I'm almost done with them. You can notice in the video some misplaced slopes, that's what I need to fix.
Wow this is awesome! 
I'd love to see some code to this.
I don't feel like sharing the whole code yet, because I'm new to programming (and thus bad at it), the code is a mess. But if you want to know how I did something specific, just ask and I'll share the code and try to explain it.
So do you use 3D geometry or how did you achieve it?
Well, I made the slopes in 3D and then render them to create the images, if that's what you meant. Using 3D is a huge time saver, because generating more terrains is as simple as appliying the image to the objects and then render, and bam, you get the whole tile set for that type of terrain.
Here's the sprite sheet to the different slopes.
Now, applying them in the correct order is the tricky part, because you need to check all six of the adyacent tiles to choose which of all these 18 slopes is the correct one. As you can see in the video, there are a lot of misplaced slopes, so it need a lot of work (which is the reason I don't want to share the executable yet).
I don't thinks so, although I wouldn't say that to non programming people, they might find it awkward. 
Thanks for the advice
Really cool. Are the elevations purely isometric, too?
Indeed, everything is isometric. I just made them in 3D and render them with an isometric camera.
As soon as I finish with the elevations I'll share the .exe so you people can check it out. If you have any terrain texture or object and want to add it to the editor just post it and I'll add it, just for fun.
