how can I make personal backround images on my youtube page? Where do i get the URL to customize my background

[you asked]

I have the regular colors on my channel/page but when I try to further customize it, I see that for a custom background I have to type in a URL....a URL from a video or cant I just use different sources? I want to use maybe pictures or patterns from elsewhere but am not sure how. Can someone help me with this? I dont want to use my own video URL by the way.