Anyway, I was trying to see what I could do with Mirc. There aren't any skins or mods available, and I honestly wasn't sure what I even wanted.
First cool thing I found (aside from the mandatory color customizations) is that you can put backgrounds into any channel window. Just right click the channel tab at the top and work your way through the menu. This isn't something I really see myself using, because it's just more stuff to load every time I click the window (I have a blank desktop, too). Even so, here it is:

The next cool thing I found was the transparent window. You can have a chat window always be on top at a set transparency level. Meaning, if you have another window focused and are clicking around in it, the chat window still remains on top. You can set this up through the options menu (alt+O) under display>windows. Take a look:

As you can see, I've clicked on the status bar to illustrate the focus thing.
This is so very close to being perfect. The only thing I can't figure out is if you can make it so that clicking in the area that the window is covering doesn't focus the chat window. Like, I'd like to have the chat window maximized on top while I browsed the interwebs and not have clicking around steal focus. As it is, letting the window sit off to the right works pretty well with my widescreen, as most websites don't cover that much space.