Have you tried this homebrew firmware with your WDTV???
I'll try to play with this once i get in touch with my old WDTV...
FROM wdtvforum.com
"This application retrieves movie content from The Movie Db and generates wd_tv.jpg, info.txt (optional), and folder.jpg files in your movie directories. These directories, when read by the Western Digital WD TV, will display a full 1280x720px background image, a 180x240px thumbnail, and movie information instead of the generic WDTV movie thumbnail and background image."
Check this complete How-To in
[color=red]http://wdtvforum.com/main/index.php?topic=3613.0[/color]