EEKeeper is not a good tool for editing anything outside the party. I'd recommend using Near Infinity instead for such things.
Note that editing the CRE file in the game's resources (RIELTA.CRE in your example) only works if you haven't entered the area they're present in yet. If you've already been there, then there's a copy of that CRE in the save instead, and you would have to find and edit that copy instead.
Comments
There's a mod for this, of course: Portraits Portraits Everywhere. Portraits for basically every NPC with a speaking role.
Note that editing the CRE file in the game's resources (RIELTA.CRE in your example) only works if you haven't entered the area they're present in yet. If you've already been there, then there's a copy of that CRE in the save instead, and you would have to find and edit that copy instead.
+1 for this mod, this and npc project make the game feel way more alive, must have mods.