Copy this into _User_MapStyles.xml and try if it works.
Code:
<ImageStyle Name="varsoon_fabled" displayname="The Fabled Ruins of Varsoon" zonerect="-322, -179, 332, 155">
<ImageFrame Source="images/maps/map_varsoon_0.dds" SourceRect="0,0,1000,512" />
</ImageStyle>
<ImageStyle Name="vrsn_epic01_boss_fabled" displayname="The Fabled Chamber of Immortality" zonerect="-234, 88, -166, 164">
<ImageFrame Source="images/maps/map_vrsn_epic01_boss.dds" SourceRect="0,0,436,506" />
</ImageStyle>