It would be nice to have some kinf of mechanism for setting Frame.setIconImage() that allowed you to specify the name of a set of icons of different sizes such that the one closest to the miniaturized size for that platform is used.

For example, if I have two versions of a miniaturized icon - 48X48 and 16X16, and they have special names in the file system or system properties (i.e. <icon_name>_16.gif and <icon_name_48.gif> and I call:
setIconImage(getPlatformIcon("<icon_name>"))
then on Windows, the <icon_name>_16.gif is used, on Solaris <icon_name>_48.gif is used. If it's called on a platform with 32x32 icons, it chooses the best one.
(This example is only to give an idea - the mechanism I described is pretty ugly - it might be better to have an idea of an icon set).

A much simpler solution would be to at least be able to get the size of miniaturized icons for the platform you are running on.