How to Add a Background to Your YouTube Channel
If you regularly upload video clips, home movies or animations to YouTube, then you may want to customize the appearance of your user channel. This is the page that other users see when they click on your name to view your uploaded videos, favorites and subscriptions. You can upload a background image to replace the default plain background on your YouTube channel.
Sign in to YouTube.
Click your username in the top-right corner of the page. Select “Channel Settings” from the drop-down menu.
Click the “Appearances” tab in the Channel Settings.
Click the “Choose File” button. Go to the folder on your computer that contains the image that you want to use as your background.
Click and select the image file. Click the “Open” button. This adds the image to the YouTube channel's background. YouTube centers the image on the page. Click the checkbox next to “Repeat Background” if you want to tile the image across the entire page.
Click the “Save Changes” button to save your preferences.