Can the band behind my banner text show a texture or picture?

Yes, on a Hero whose Single Image Layout is Image Beside Text. Open the page in Website Builder, select the Hero block, open Config and choose a picture under Photo behind this block. It fills the band behind the words, for example a paper texture in your brand color. The Scrim setting under it puts a wash over the picture so the words read: it darkens the picture for white words, or lightens it for dark words when Lighten image is ticked. Slide it to 0 for a texture that is already dark. Under Content, Picture Description is what a screen reader says for the Hero's picture, and what search engines read for it.