A while ago I wrote a lengthy article here about my struggles to become a YouTube partner. When I was done with that several-pages-long piece of work, I realised that it was wholely about me whining and held no entertaining content whatsoever, so I deleted it again. Plus I actually did gain partnership shortly after. However, becoming a partner granted me only few of the promised advantages, the most important of them being: individual thumbails.
Seriously, people: this was the main reason for me to become a partner and it was absolutely worth it! Creating interesting, personalised thumbnails for each video has become one of my new favourite things related to my LPing career. It's so satisfying to have a little piece of art smile back at you, advertising for your videos instead of the random convoluted piles of mess YouTube offers non-partners as thumbnails. It looks a lot more professional (though the content of the videos certainly didn't improve) and attracts viewers much more efficiently than any exciting title ever could.
However, as Spiderman's uncle said: with great power comes great responsibility. Theoretically I could create any thumbnail I wanted. Of course, what comes to mind first are half-naked women pushing their various humps into the viewers face. Research has shown that YouTube viewers do indeed instinctively click on these videos more often than on others. And in fact I have done just that... twice now. Once for a Thief 2 episode named 'Hookers' because of a supposed hooker I knocked unconscious and then once more for my Gothic Erotica video, where I featured the in-game picture of a half-naked lady. So you see that - though I had the opportunity - I used this cheap trick only on videos where the thumbnail accurately descripted the content of the video... and not just to generate views and distract from my lack of humour/entertainment/general purpose in life. Don't want to point fingers here, but since you're all familiar with YouTube there's a good chance you know who I'm talking about. Gosh, how I dislike that guy. Goes to show that the path to the dark side is way easier to travel.
Another tricky thing about thumbnails is that you can't just march off into the depths of the Internet, grab any picture you like, drag it back home and then alter it for your purposes in order to create some fancy thumbnail. Generally speaking, EVERY picture is protected by copyright. Using it without the explicit permission of the owner is actually a crime. There are some ways around this problem, however. Of course you could just ask an artsy friend to draw all the thumbnails for you or give you permission to use their work and attribute them in the video for it. If you have an artsy friend, of course. And if they are willing to work for your benefit just like that. OR you could check out the huge database of royalty-free images available at various websites (wikimedia is my personal favourite so far). You still have to check every image you find there for its specific copyright status, but most of them are free to download, alter, distribute etc without having to credit anyone or being worried that the NSA sells your criminal arse to the local authorities. Or, in turn, uploads your private pictures on their website without your consent...