SET_PORTRAIT turns out not to be necessary.

data/campaigns/Northern_Rebirth/scenarios/Breaking_the_Chains.cfg

@@ -77,6 +77,7 @@
 	[side]
 	type=Peasant
 	description=Tallin
+	profile=Tallin.jpg
 	[modifications]
 			{TRAIT_RESILIENT}
 			{TRAIT_INTELLIGENT}
@@ -154,7 +155,6 @@
 
 	# Override Tallin's team color so he has a distinctive purple shirt.
 	{TEAM_COLOR_OVERRIDE description=Tallin 4}
-	{SET_PORTRAIT "Tallin" "Tallin.jpg"}
 
 	[unit]
 	type=Peasant

data/utils/utils.cfg

@@ -417,25 +417,6 @@ name=prestart
     [/unit]
 #enddef
 
-#define SET_PORTRAIT DESC IMAGE 
-# Set the profile field of any unit matching specified description.
-# Meant to be called in a scenario start or prestart event.
-# This change will be persistent and carried by the unit in later scenarios.
-	[object]
-		silent=yes
-		duration=forever
-
-		[filter]
-			description={DESC}
-		[/filter]
-
-		[effect]
-			apply_to=profile
-			portrait={IMAGE}
-		[/effect]
-	[/object]
-#enddef
-
 # FIXME: Documentation for these is needed.
 
 #define MENU_IMG_TXT IMG TXT