This new method makes the portraits fully compatible with NBA Today, meaning that you don't need to touch the roster file.
Ok, lets get this going.
First of all, I've used Mr X and subsequently solovoy's file for extracting what I needed. I suggest restoring the portrait.cdf/iff and portrait_hi.cdf/iff back to the originals. I've already exported the dds for missing portraits, plus 4 additional portraits for players yet missing from the official rosters. The rest of the modified portraits it was too much work, ask Mr X or solovoy for the dds.
The first thing to do is to open portrait and portrait_hi with the mod tool to decompress them. Then install the tool called "Total installer thingy for MLB 2K10" that a guy by the name of krawhitham created for MLB but it works with NBA with a minor thing to do. That minor thing is that MLB has no portrait_hi file, so the tool installs the dds only to portrait.cdf. We can fool that by taking portrait_hi and removing _hi. Now it comes to you to decide which file to use, portrait_hi or portrait. If you're playing with high or medium settings you are using _hi, the other is not needed. If not, disregard the following. Delete portrait.cdf and rename portrait_hi.cdf to portrait.cdf and delete portrait_hi.iff.
Now launch TiT 2010 and select the NBA 2K11 installation folder. Now select the file portraits.7z and press "Start" and wait for the process to finish. Once finished go to your NBA 2K11 installation folder and you'll see a folder called portraits which is a left over of the process and is safe to delete, also you'll find some .bak in the portrait files that are safe to delete.
Now if you went for the _hi take portrait.iff duplicate it and rename it to portrait_hi.iff and that's it. If you went regular, then that's it, enjoy.
One minor bug and that is 2ks fault is that some new players in the roster use the id of some of the fake classic players, so in those teams for some fake players you'll see the portraits of the new players.
For creating new portraits its very very easy. Just save the dds with the target portrait id as a name, for example, 1905.dds. Then run the tool called portrait-builder that comes with TiT select the folder where the dds files are and you'll get with a file called mlb2k10.7z install that file with TiT and that's it.
Download the pack here, it contains the tool, and the portraits plus the additional ones.