I usually pick up a paid theme. I use PixelExit for XenForo and Sultan Themes for vBulletin.
Most of the time, you can customize premium themes easier and make them feel like your own.
I considered getting a custom theme by PixelExit. It starts at $1,500 a theme, and that's not the amount I wish to pay. But I'm not knocking them. I'm sure it's worth that but I just don't want to invest that much into a forum when their regular premium themes are good enough.
I'd love to learn how to make a theme myself. I need to do that.