If you want to save something as .jpg you can start off by opening the file. Then go to File -> Save As...
A dialog box will appear prompting you to save the file. At the bottom of the dialog box (below the name of the file) is a small combo box (similar to a dropdown menu) that says .tga. Scroll down on that little combo box until you find .jpg or Jepeg. Select that and it will save the file as a .jpg image when you click save.
@Jirinal: Your absolutely right, it is always better to place them by hand. But sometimes the doodads stack up and the only way to move them is with the number pad (without messing with whats around them of course)
Edit: I just downloaded your map and had a thurough look over it.
Some Suggestions:
Place doodad 1 at a time and rotate them accordingly.
Play around with terrain heights and weather effects more
Dont over-use the same doodads too much
You can customize doodads and destructables to create some nice effects
Try to use doodads from a certain tileset on your map (you have a random tree covered in snow surrounded by whales and seaweed in a square of water)
Try to incorporate as much realism as you can in your work.
Take screenshots that show the best parts of your terrain and leave out parts that look less favorable (I took 2 screenies from your map - see attached)
Some good things about your map:
Originality of the dragon-titan attacking the city
The city has a simple, yet eye pleasing layout
the idea that there are only orcs in the city creates the effect that the city is under quarentine (or some sort of forced control)
We all started off about the same, nobody here started off terraining floating bridges and trees that lay sideways on slopes with units fighting ontop of them. In short, dont let my criticism get you down, its all for your benefit. Good luck and happy terraining