The base code for leveraging MPAA ratings is there in the latest release: Search for "VideoMPAAFlaggingConditions" in "skin/Confluence/720p/IncludesCodecFlagging.xml" to see the code.
However, most views don't seem to call and display the MPAA images. I saw that one of the views (PosterWrap2Fanart) was displaying the rating. So, I found the code calling it and I made the following mod for "PosterWrapView", so the MPAA rating shows up. You should be able to make this same mod for whatever view you like best. The only trick is finding a good place to display the rating. You will see in my example the location I chose, but it can be placed pretty much anywhere.
Backup ViewsVideoLibrary.xml
Edit ViewsVideoLibrary.xml
Find so your modifying the right view, in my case I am modifying Poster Wrap: include name="PosterWrapView"
Scroll down till you see:
<control type="grouplist">
<description>Media Codec Flagging Images</description>
<posx>0</posx>
<posy>620</posy>
<width>1280</width>
<align>center</align>
<itemgap>0</itemgap>
<orientation>horizontal</orientation>
<include>VideoCodecFlaggingConditions</include>
<include>AudioCodecFlaggingConditions</include>
<include>AspectCodecFlaggingConditions</include>
<include>VideoTypeHackFlaggingConditions</include>
</control>
Add the following code after the code mentioned above:
<control type="grouplist">
<description>MPAA Rating Flagging Images</description>
<posx>700</posx>
<posy>590</posy>
<width>800</width>
<align>center</align>
<itemgap>0</itemgap>
<orientation>horizontal</orientation>
<include>VideoMPAAFlaggingConditions</include>
</control>
The following is the result. Notice that the MPAA rating is floating in the bottom right corner. Again, you can add the MPAA rating pretty much wherever you want, but I chose this location.