I recommend that your account picture (which you set through your Google account) is some sort of brand logo. If you’re a one-person business, it can be a professional headshot of you. Ideally, it should match your profile pictures on other social media accounts for instant brand recognition. This works both ways; if ones of your followers from another site comes across your YouTube, you want them to recognize you so they’re more likely to watch. And, vice versa, if a viewer Googles you, you want them to be sure that the Facebook profile they’re clicking on is actually you. To change your channel art, just click on it when editing your profile.
Yeah. The concern from an SEO perspective is that YouTube, their goal is to keep people on YouTube for as long as possible, watching as much content as possible, engaging with as many videos as possible, seeing as many ads as possible. And so if your video ends the viewing session for a viewer, like they watch your video, then they click on that link and go to that company’s website and buy the product, that’s great for you, but your video could potentially not perform. If everyone who watches the video took you up on that offer, your video could potentially not perform as well as it otherwise might.
To make your YouTube channel private, click on your avatar icon in the top right corner of the screen and select Settings. Open the Privacy tab and click the appropriate checkboxes to set the privacy settings as necessary. For example, you can make the channel videos private, keep all your liked videos private, and so on. You can uncheck those boxes anytime to go back make those items public again.