There are a number of new skinning features that come with the new QMP (QCD v5) player. The most notable one is the Media Library. Other minor additions are support for album art and a skinning control for maximizing the player.
This is one of the last things you want to make when creating a QMP skin. Skinning the media library can be tricky but it all depends on how you approach it. There is one bitmap that needs to be created. This is the MLset.bmp. The controls in it have been subject to change from previous builds and instead of naming them all just have a look in the new QMP skinning how-to documentation. A method that really works well is to create the Media Library in your paint programme first using lots of layers or at least multiple layers for the button states in the Library. When done, open a pre-existing ML ripped from another skin and systematically start changing the elements. If you don't know where a particular element comes from, open that original skin in QMP and have a good look. But again, you should be able to find all the details in the skinning doc.
The other file that comes with the media library is the configuration file MLskin.ini. This one is pretty confusing (even I have to admit). Just start by changing one line at a time after taking it from a pre-existing skin and see what has changed when you package your skin and open it in QMP. Be patient! That's the key. Just don't rush this! No matter how pretty you skinned the ML, it'll look crap if you just take the default settings.
To implement album art in the skin, just colour a region in the colour map (be it the main window or an extension map) with this colour: 153,0,255
Maximize: 0,0,204
Mixer Channel: 204,34,17
Pre-amp Slider: 238,238,170
Auto-pruning: 153,204,102
Manual advance: 153,204,153
Browser forward: 51,0,255
Browser back: 68,0,255
Browser stop: 85,0,255
Browser refresh: 102,0,255
Open library window: 102,204,255
Fullscreen video: 51,153,204
Title bar control (db click to maximize): 153, 0, 204