some may already know about this,but for people who don't, here it is:

worldpainter,an amazing terraforming program,has a feature to import an image from your computer,and make it into a minecraft world - The darker bits of the image are low bits in the world,and vice versa


What To Do:

1. Click 'file'
2. a drop - down menu will apear. hover over the option that says (i think this is it) 'import world'.
3. another sub - menu will appear witgh 2 options. one is 'import existing minecraft map'. the other is 'import height map'. click this.
4.a window will open showing your files. select the picture you want.
5.enjoy!

it is amazing!

here is a link to download worldpainter:
http://www.minecraftforum.net/topic/231255-worldpainter-new-map-creatorgenerator-work-in-progress/