You could use an .pak extractor (https://dl.dropboxusercontent.com/u/32263228/lstools.zip) and extract the Textures.pak, inside the 'Divinity - Original Sin/Data' folder and then search for the "Portraits_MainPL_CP_Icons.dds" file yourself, and then edit it.

I'll upload my own edited file here.
http://www.mediafire.com/download/iovgtwdm15dlmc5/Portraits_MainPL_CP_Icons.dds

You can then edit it yourself (There are plenty of ways to do it, you could use a converter to .png or a software capable of opening and editing the file. https://www.google.com/?gfe_rd=cr&ei=Ic0YVOmwC6Ok8we6QQ&gws_rd=cr#safe=off&q=.dds+editor).

Then just put the edited file in the 'Divinity - Original Sin\Data\Public\Main\Assets\Textures\Icons' folder. If you don't have that folder already, just create it.