I'm still not the best at it, and using GIMP over Photoshop probably isn't the best idea either. But hey, you can't beat free right?
I drew up custom avatars for me and the people in my team (some are still a work in progress) and a logo that I put in every thumbnail, or at least most of them.
I don't always have the best font choices, but they've definitely come a long way from how they used to look.
I think the biggest thing is finding your own niche so that people can easily tell that its your video.