This is my second chat skin, and it actually looks somewhat good. 8P
Copy the code from here into your /common.css: http://heliosanctus.wikia.com/wiki/MediaWiki:ChatSkin_Planet_Neutral.css. After that, you have to reload the cache, so go ahead and press CTRL+F5 if you're on windows, or CMD+Shift+R if you're on a mac.
And then you're done!