What does "Ship Trap island" from the story "The Most Dangerouse Game" look like?

What you are asking is a question about the setting for the story "The Most Dangerous Game."  The story is not EXACT in its description of the island, but I do think that enough information is given in the text to make a pretty good guess at the layout of the isle.

To do so, let's head to the text with a few choice quotes, shall we?:

"OFF THERE to the right--somewhere--is a large island," said Whitney." It's rather a mystery--"

"What island is it?" Rainsford asked.

"The old charts call it `Ship-Trap Island,"

This tells us two important facts...first, the island is "large."  Now what does this mean?  Large is a very subjective term and means different things to different people.  Well, from what we can tell from reading the rest of the story the island must be big enough to support life but not so big that people try to go there a whole lot (which would ruin the creepy guy's hunting plans.)  In addition, he gives the person a three hour head start.  If the island were too tiny, three hours would be too much (where would there be to go?)  So the island must be of decent size.  Gilligan's isle?  The island from Lost?  probably something in between those two.

the muttering and growling of the sea breaking on a rocky shore... Jagged crags appeared to jut up into the opaqueness

So the shore of the island is not a nice sandy beach, but rather jagged sharp rocks.

Dense jungle came down to the very edge of the cliffs..

So, apparently, the island is covered by thick jungle.

there are jungles with a maze of traits in them, hills, swamps--

Again, there must be some hilly parts, and some swamps.

the general pressed a button, far out to sea Rainsford saw the flash of lights

As a trick, the island has a string of lights in the water that make it look like there is a safe channel for boats, when in reality it leads to the sharp rocks.

His eyes made out the shadowy outlines of a palatial chateau; it was set on a high bluff, and on three sides of it cliffs dived down to where the sea licked greedy lips in the shadows.

The only man-made structure, apparently, is "The General's" house.  It is on a hill where three sides of the hill are cliffs that lead down to the sea.

Well, that' all I've got out of the story.  I half expected to read that there was a giant, skull shaped mountain in the middle to make it even more spooky.

Good luck!