You have to mess around a bit with the name if it doesn't work at first. The last time it didn't work I actually fixed it by removing one letter from the name (so 6 characters + L, instead of 7 characters + L). It seems that it doesn't always work if you use numbers, signs or capital letters in the name. I sometimes have problems with getting an L and M portrait with the same name to link together. You can simply replace the M with an L in the filename though if it has a large enough size. Only putting an M portrait in the portraits folder will not work. You can also just use an L portrait, it will just show up everywhere. Now, Ive tried saving the original save file and exporting it and then importing it in to the Enhanced Edition, but when I get into the Enhanced Edition and click import the save isnt there.
This means that your portrait on the right side of the screen and in the chat window will use the M portrait (instead of S) and the character screen will use the L portrait (instead of M). Im trying to import a character from the original Balders Gate into Balders Gate Enhanced Edition. The M size will not show up during character creation, but will be linked with the L portrait of the same name automatically (instead of manualy like before).