[pkscout]

However .. I am struggling with the ability to have my pictures "sized" so they fit into a 1080 screen

I have tried placing a file "advancedsettings.xml" in Kodi/userdata

<advancedsettings>
<imageres>480</imageres>
<fanartres>480</fanartres>
</advancedsettings>

But it does nos appear to have any affect ..

How the pictures are displayed is a skin level thing, not a global Kodi thing. You could check with the authors of the skin you're using to see what the say. You can also change the way the images are displayed by modifying the skin. All the non-default skins are stored in your Kodi user data directory, so once your there go to addons->skin name->xml and find the file named MusicVisualization.xml. In there you'll find something kind of like this:

Code:

<control type="multiimage">
    <left>0</left>
    <top>0</top>
    <width>100%</width>
    <height>100%</height>
    <imagepath colordiffuse="88FFFFFF" background="true">$INFO[Window(Visualisation).Property(ArtistSlideshow)]</imagepath>
    <aspectratio>keep</aspectratio>
    <timeperimage>10000</timeperimage>
    <fadetime>2000</fadetime>
    <randomize>true</randomize>
    <animation effect="fade" start="0" end="100" time="400">WindowOpen</animation>
    <animation effect="fade" start="100" end="0" time="300">WindowClose</animation>
    <visible>System.HasAddon(script.artistslideshow) + String.IsEqual(Window(Visualisation).Property(ArtistSlideshow.ArtworkReady),true)</visible>
</control>

The width, height, and aspect ratio are the things to adjust as needed. Here's a link to the explanation of the aspect ratio options:

http://kodi.wiki/view/Aspect_Ratio