if you mean (main and frame) borders are for other purpose
Seriously??
Let's try that again, I assumed too much:
From your MC installation folder, go to "Data\Default Skin Items\Standard View"
In there, you will see three files named:
Border_DropShadow.png
Border_Frame.png
Border_GlowShadow.png
These files draw the frames and shadows around list items in thumbs mode.
List_Selection.png simply marks that entire space as 'selected'.
You can copy these files to your own skin, and then, use the "<BORDER>" section in your own xml to manipulate their behaviour.
<BORDER>
<Entry Name="GlowShadow" Bitmap="Border_GlowShadow.png" Rows="5,?-Flex,9" Columns="7,?-Flex,7" Cells="B2-Skip">
<Data InternalMarginLeft="5" InternalMarginTop="3" InternalMarginRight="5" InternalMarginBottom="7"></Data>
</Entry>
<Entry Name="DropShadow" Bitmap="Border_DropShadow.png" Rows="3,?-Flex,7" Columns="5,?-Flex,5" Cells="B2-Skip">
<Data InternalMarginLeft="5" InternalMarginTop="3" InternalMarginRight="5" InternalMarginBottom="7"></Data>
</Entry>
<Entry Name="Frame" Bitmap="Border_Frame.png" Rows="7,?-Flex,11" Columns="9,?-Flex,9" Cells="B2-Skip">
<Data InternalMarginLeft="9" InternalMarginTop="7" InternalMarginRight="9" InternalMarginBottom="11"></Data>
</Entry>
</BORDER>
The 'slightly off-center' thing has been there a looong time.
Personally, I pushed for separate "List_Detail_Selection" and "List_Thumb_Selection" images as I found it limiting having to strike a balance that worked for both view styles in a single selection png file.