[QGIS-Developer] Setting path to an icon

[Pat Hin]

Hello,

i have successfully linked my self written script for the processing toolbox as a button
to the main menu.
Now i would like to link a an own image/icon to this button. Under general options for
the processing toolbox there is a field for "icon" so i suppose in this field i could
set sth. for this.

So my questions :
a.. is this right?
b.. what exactly do i have to enter in this field?
c.. what are the restrictions for an own icon? pixel, size etc?

many thanks
pat