Is there any way to change the NPC portraits in Baldur's Gate. I also have TOTSC installed. I want to switch them with Icewind Dale portraits. Any and all help would be appreciated.

I know very little on this subject, but from what I have heard, importing the Icewind Dale portraits to BG1 or 2, is nearly impossible. I guess the formats are incompattible.
P.S. (You might take some heat for this, but if I were you, I would post this question on the General forum. There are alot more people on that forum who are into graphic design and other realated areas of Computer Science.)

You might have to do it with a graphics editor--export the IWD pic to a general file, load that file in your graphics program, crop, convert to bitmap, save.

Over and over and over.