Well spawning means an object created by another object, so you will need to clarify if you want it spawned, or created by the system.
Either way you can get a ranged random from normalrandom().
As a spawn:
+>Island spawn object tree
->tree set position to island.x + normarandom(0,xmaxoffset), island.y + normalrandom(0,ymaxoffset)
As system create:
+>system create object tree at island.x + normarandom(0,xmaxoffset), island.y + normalrandom(0,ymaxoffset)
Then you can take that farther by using numbers as image points with random.
+>set global.value("rangen") to random(4)+1
->+>system create object tree at island.imagepointX(global.value("rangen")) + normarandom(0,xmaxoffset), island.imagepointY(global.value("rangen")) + normalrandom(0,ymaxoffset)
Given you have set up 4 image points numbered 1-4 on the island.