WD developers decided to make the “focused” icon area not support alpha transparency (which is why you see the “black box”)
Even if you make the focused icon eg. main_videos_icon_f.png a transparent png, it will still display with no transparency.
2 WORKAROUNDS
1st Workaround: Design the focused icons eg. main_videos_icon_f.png to contain a part of background and it will blend in main background.
Examples:
http://community.wd.com/t5/WD-TV-Live-Hub-Themes/ALASKA-RESURFACE-REMIX-LIGHT-DARK/td-p/327445
http://community.wd.com/t5/WD-TV-Live-Streaming/TITAN-LIVE-New-Theme-Now-Available/m-p/640939#M25868
2nd Workaround: Removed the focused icons (done by resizing them to 1x1 pixels) which then leaves the non-focused icons to display with full transparency (but there will be no ‘pop-up’ or focus of the middle icon. The example below contains a back color focus that appears through the non-focused icons)
http://community.wd.com/t5/WD-TV-Live-Hub-Themes/My-Aeon-ish-Home-Screen-Experiment-Info/td-p/171368
Here’s the focused icon (a tiny 1 pixel dot)
