Well, thanks to
Odaku's post I got it figured out. Here's the bigicons zip. The icons are kind of grainy at 1600, due to the resize. Because of some hardcoding limitations, I was only able to double the size, where I would have liked to have them a bit smaller than double. This is the horizontal version as default, with vertical format also in the zip, just need to rename it.
OK, the enlarged gem .tgas are too big to attach. If you have graphic editing capabilities, open up the 2 default gemicon.tgas and resize them to 512 512, then save them. If you don't have a .tga editor, try using the tgas from Odaku's page with these .xmls
Hope this works for you
Lunakin