You can already easily change mIRC to look the way you want. Other than getting someone to make you a theme, what are you looking for that isn't already easily done? Try searching for MTS themes and you'll probably find a dark theme already made that will work fine in the current version of mIRC. And even if you can't, it's very easy to adjust colors and such. It's also easy to adjust the toolbar icons if you want to do that, though it's less straightforward.
