I am pretty sure, but other forum users feel free to correct me, the background of the 3D heads is from the Haptek player used.
I have been also making new skins so I've had do do some of what you are speaking of. You can make areas of your skin transparent yby making the color R:255 G:0 B:255 and saving it as a bitmap. It can be a bit tricky to get all of the background color (which is going to be used as a mask)to that color with outit bleading into the part that you want to be see. I turn off all anti-aliase when you make the mask for the object.
I then downloaded the Transparency Mask Creator in on the pluggins page:
http://www.ultrahal.com/files/detail.asp?iFile=196&iType=18It make a mask mapping from the bitmap tha you create that you have to add to your skin file.
I hope that that helps you out some.