I decided to post all the emoji from the iphone emoji keyboard on my Facebook status to see which ones would be displayed in the iphone App.
Even though you can type in any iphone emoji you want when updating your status and can even actually post your status with any iphone emoji in it without getting an error, many of the emoji don't actually display in the iphone app when you refresh it to see what you posted.
The image in this post shows all the emoji that I was able to see in the Facebook iphone app after submitting my status. NOTE: Unfortunately, what emoji you can see depends on what you are viewing Facebook with. Below is what you can see in the iphone App, but when I checked it with the Google Chrome desktop browser, very few emoji were displayed :-(