Thanks @joyrider3774 & @Tom Speirs.. I turned off media matching and it fixed it.
This is in Game Manager..
The wheel images are named "R-Type (Irem 1987).png" & "R-Type II (Irem 1989).png", so it all seems logical that it works.
Excerpt from mame.xml
<game name="rtype">
<description>R-Type (Irem 1987)</description>
<rom></rom>
<manufacturer>Irem</manufacturer>
<year>1987</year>
<type>Arcade</type>
<hidedmd>True</hidedmd>
<hidetopper>True</hidetopper>
<hidebackglass>True</hidebackglass>
<enabled>True</enabled>
<rating>0</rating>
</game>
<game name="rtype2">
<description>R-Type II (Irem 1989)</description>
<rom></rom>
<manufacturer>Irem</manufacturer>
<year>1989</year>
<type>Arcade</type>
<hidedmd>True</hidedmd>
<hidetopper>True</hidetopper>
<hidebackglass>True</hidebackglass>
<enabled>True</enabled>
<rating>0</rating>
</game>
However, once in PBX it shows up as
But with Media matching turned off, it's all fixed..
I'm sure you can understand my confusion. I've found other oddities with media not working as intended (but can't remember specific examples), so hopefully this should now be fixed.
Thanks again all.