rv_preview_browse_page.xml : preview with a list to the left.
rv_video_browse_page.xml : 4 x 4 grid
rv_large_video_browse_page.xml : 3 x 3 grid
rv_list_browse_page.xml : 2 columns, 8 rows each, shows thumbnail for selected item
rv_gallery_browse_page.xml : a row of 7 covers, shows metadata
rv_list_browse_page.xml : see video
rv_music_browse_page.xml : a 4 x 3 grid
As you can see, video and music (and photos too by the way) share the rv_list_browse_page.xml.
It’s best to download the Legacy theme from WD first and have a look. It has most files, but I have to warn you: it’s not complete. Wd doesn’t want you to mess with the services, and for instance is the accu_weather folder missing from the Legacy theme. The only way to get hold of the complete Mochi theme is to extract it from the firmware update file.
For the weather and time, I rewrote decoration.xml. You can find it in the Mini theme thread under “Weather and Time mini mod”. Try it out
You only have to supply the files you altered for your theme, the Hub will use the files from the built in Mochi theme for everything that’s missing.