Let me know what format and size the file should be, and I can send you one right away.
I'm realy not the right person to ask about this!
Personaly I would prefer svg format (scaleable vector graphics and this looks best) about 50 x 50 ppi, but png format could do it as an alternative.
I have tryed the windows version og HE through Wine. The icon delivered with HE windows version worked fine with Ubuntu 10.04. I don't know format and zise but I think a migration of the icon without any change will work fine also.
Maybe I should mention that the icon will be used to make a nice shortcut to HE instead of an default maked by the system.