I was going to edit Arazlam's portrait for one of my projects. But I realize now that I have no idea how. It doesn't seem that his potrait is something that Shishi can edit.
Alazlam, Aeris, uniques with generic sprites (Golagros, Miluda, etc), and the like have their portraits stored in WLDFACE.BIN, since they aren't full sheets. To edit any of them, you'll need FFTEVGRP (http://ffhacktics.com/wiki/FFTEVGRP) instead of Shishi. You can follow Celdia's tutorial linked on that page if you get lost, though said tutorial is for the more in-depth act of replacing formation screen graphics. To speed you along, Alazlam's portrait is 0x77.