From the jfxopen list:
Subject: Ant-Task-Documentation
Date: Tue, 10 Jul 2012 23:07:47 +0200
From: Tom Schindl <tom.schindl@bestsolution.at>
To: openjfx-dev@openjdk.java.net <openjfx-dev@openjdk.java.net>


Hi,

I'm just working on IDE support for fx-ant tasks but the documentation
for things like fx:icon and fx:splash is a bit sparse (see
http://docs.oracle.com/javafx/2/deployment/javafx_ant_task_reference002.htm#CIAIEJHG).

The biggest mystery for me what effect fx:icon what width/height/depth
combination are expected to be set?

An educated guess from my eclipse applications is:
16x16 8bit
16x16 32bit
32x32 8bit
32x32 32bit
48x48 8bit
48x48 32bit
256x256 32bit

What are the icons used for (where do they show up)? What are the
supported formats (guess is png,jpg,gif)?

Tom