Try this link:
Creating HTML Image Maps
Consider working with the polygon shape, which may be excellent for tracing out approximate coastlines and borders.
It'll give you the following example (which may be enough):
<img src="trees.gif" usemap="#green" border="0">
<map name="green">
<area shape="polygon" coords="19,44,45,11,87,37,82,76,49,98" href="http://www.trees.com/save.html">
<area shape="rect" coords="128,132,241,179" href="http://www.trees.com/furniture.html">
<area shape="circle" coords="68,211,35" href="http://www.trees.com/plantations.html">
</map>