Yea, there's no volume control. I usually use keyboard shortcuts for that. As for your problem with coverflow - I wish I could help you but I haven't looked at the code for eeeFoo or even used it for a long time. Support for paneslui (component used for the skin) has been dropped.
When I feel like it, I might port it for columnsUI.
The foobar developers made some rather big changes which broke support for panelsUI. It wasn't really an attempt to stop all the customizations persay.
I still use foobar, but use the columnsUI and panel stack splitter components to fiddle around with my user interface. Some people have released some really good configurations. You can find them here on deviantart under Customization\Skins & Themes\Media Players\foobar2000