The quality of your portraits are fine to me and they look very nice in the game. You don't need 3000x2000 (or whatever) foto to do a dds as the game uses only 256x256 pictures. So don't worry about that
I have a question. If we're able to add 65 thousands of portraits in the game, does that mean if I create a dds file, give this file "10000.dds" name, open roster editor and set a portrait number of a certain player to 10000, this player will have created portrait?