It might seem odd to see me say this (beacuse I know Andy's post is directed at me) but he makes a good point, trust me, rushing a map doesn't help even if you end up with the balance right is more work then it's worth fixing mistakes once it's up. In addition I'd like to recomend some programs for people who would like to make maps but currently only have paint installed on their computer.
The Gimp (http://www.gimp.org
) This is an open source alternative to photoshop. Since it's open sourced versions are available in most languages for every operateing system. There are tons of online forums and tutorials which will help you learn everyaspect of this program. My advice is to learn the power of the path tool, it's all to often over looked but it offers a very easy way to draw perfectly even lines, even if you aren't artistically inclined.
) I've seen the term vector graphics thrown around alittle here, for those of you who don't understand the diffrence between vector graphics and pixel graphics don't worry. Inkscape while tricky to use provides a free alternative to programs that sell for several hundred dollars. Like the Gimp it too is open sourced which means that it will run on your computer, no matter what operating system your running.
Blender 3d (Blender3d.org) For those of you adventureous enough to consider doing some 3d modeling as part of your map creation this would be a good start. Alternatively if you don't know how to model in 3d it's always a good time to learn how. Blender is by far the best open source 3d modeler available, it can do anything that programs costing several thousand dollars more can. Again there are tutorials available if you find yourself lost in the interface (you will).
All the programs listed above are totally free, most of them are pretty intuitive once you get past the inital learning. I'd also be willing to post a map making 101 if anyone is interested, I'm sure other mappers would be willing to help.