Change icon for all files of a given type

[JohnAtl1]

I've been googling for quite a while, and there doesn't seem to be a definitive answer for this. I have files with a .tap extension, which I've set the default app to be Textmate for. Some of these files have a shell executable icon, some a blank page, even though they all have a .tap extension. I want to change them to some icon representative of what they are. My second choice would be for them to have the Textmate icon.

Surely there is a shell command or some way to change the icon for all files of a given type.

Thanks,
John

OS X 10.9.3, Mavericks