The dacian flag now looks closer to the original. The modders interested in changing the awful flag from Paradox may download the repainted flag from here http://www.tgw1916.net/rome .
If you like it then extract and replace DAC.tga file in \gfx\flags folder.
I changed it in my game with no problem at all.
(Paradox used compressed tga 64x64 so, if you want to redraw a flag, you need to get a graphic editor that can read compressed tga. Ordinary editors just show garbage. Happened to me.)