TRoW: [unit]image= is not supported

We should really use a custom unit type to get the desired effect;
however, that could cause out-of-sync errors, so for the 1.14 branch
we instead replace the image via an [object]

data/campaigns/The_Rise_Of_Wesnoth/scenarios/16_The_Kalian.cfg

@@ -50,6 +50,14 @@
         team_name=Elves
         user_team_name=_"Elves"
         {FLAG_VARIANT long}
+        [modifications]
+            [object]
+                [effect]
+                    apply_to=image_mod
+                    replace=O(0)~BLIT(units/kalian-elvish-champion.png)
+                [/effect]
+            [/object]
+        [/modifications]
     [/side]
 
     [side]