Open
http://ip_of_your_player_here in your browser. The homemenu replacement module should allow you to hide YT button. It's down in the list of options.
The 1st question (subs prefs) doesn't have a fix right now. Not for iconbit skin nor for most of the other skins that look a bit like iconbit. Can't recall their names.
And the 2nd question I honestly don't know. I use whatever background image that comes with the skin.
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For me iconBIT is the best but it is missing a few minor details:
- remembering subtitle preferences
- subtitles that can show italics and bolds instead of <i>blabla</i> or <b>blabla</b> (this bug covers all skins IIRC)
- play subtitles over DLNA/uPnP sources (this feature is missing on all skins IIRC)
- having a small web browser (IIRC it's only available on the o!play mini FW)