It is importnat to be able to develop tunable custom progress implementations and sometimes tuning could be dynamic.
E.g. one may dynamically chose which logo and what background needs to be used on this particular web page.

For example this is particularly important for someone who wants to redistribute FX gadget and does not know where it will be deployed.

We need to support 2 ways:
  - ability to access JNLP properties from custom progress
  - ability to access applet parameters (or something else that can be controlled from javascript)

We may also want to expose delay before custom progress is shown as public property.
E.g. if someone wants to reuse custom progress to include application startup time then he may want custom progress
to be shown immediately (not after delay).