I have a 2014 WDTV Media Player … so this info is not a guess
Any Theme for the WDTV Live Streaming (SMP) will work with the WDTV Media Player (2014) *they are identical hardware*
Almost all themes a modification of “Mochi”
the “Grid” theme which is a newer interface has very few Theme edits
Except my “PM4 WD” Theme which is a Modification of “Grid”
http://community.wd.com/t5/WD-TV-Themes/PM4-WD-Project-Mayhem-for-WDTV-Theme/td-p/792197
My other Theme “Alaska Resurface” is a Modification of “Mochi” … it was written for the WDTV Live Hub, but works fine on the WDTV Live Streaming AND the WDTV Media Player (2014)
http://community.wd.com/t5/WD-TV-Themes/Alaska-Resurface-WDTV-LIVE-HUB-amp-SMP/td-p/327445