Some comments for my skin:
If you want to have shadows, yo need to use Ubuntu with compiz. Thats the reason why the borders are squared, because if not, shadows won't appear. It would be great if you repair this bug.
Another point is that I can't understand why in Mac Os they have such a beautiful skin for VLC while in Windows and specially Ubuntu we can't enjoy that. We need a conversion for that skins with transparencies and full shadows and also for full screen. It's not enought to have the gtk look only. So, for doing it the best, port mac os skins of VLC to the rest of systems.