Custom Media Library Genre Thumbnails

I have movies on several different external drives (e.g., DVD on 1.5 TB Element, Blu-Ray on 2.0 TB Element) and I like the Genre Filter that is built into the Media Library.  I understand how to set a thumbnail on a folder (folder.jpg), and I know I can set up my own genre folders and work it that way, but they would be drive/folder specific.  I like that the system genre folders merge all movies from all folders into one.  The system genre folders are erratic… some show a thumb from one of the video files, others do not.  Most of my files are ISO, but I am still in the process of converting all VIDEO_TS and BDMV folders to ISO, so some folders contain both at this time.  I’m not sure if that is the culprit of the inconsistent display.  More so, I really would like to use a Genre Thumb, rather than a movie thumb.

So, in short, can we customize the system genre folders and if so, how?

Thanks!

Joe

follow up question on movie genre folders; my XML files have multiple genre listings (e.g., one movie may be Action & Drama).  However, the Media Library only uses and displays the first genre listed, which is suboptimal; it should list all  (like it does all actors), and display in all matching genre listings.  Is this a bug in WDTV, or is it just a system limitation?  Any known workarounds?

Thanks again!