UPDATE:Since the newest Spotify versions 0.8.8+ the client uses a lot of web-based elements, which I sadly can not change with my methods. That's why I gave up on custom skins. So this here now, is just a gallery of what was possible before. If someone finds out how to change the new elements, feel free to contact me here. 😉
Also you can check out my darker skin for the WebPlayer here.
@AnRchi Glad you like them! Unfortunately those skins dont work anymore. I stopped updating them when Spotify introduced more and more html elements (version 0.9.0+) that sadly cant be changed with this method.
The message you're getting sounds like a new bitmap file cant be loaded because its not inside my changed old resources.zip file.
If I will ever find a way to manipulate the new webbased elements I will start again to create new skins. Meanwhile you can check out my dark webplayer skin from the link in my signature. 😉