I listen to some fairly obscure Progressive Rock bands. Is there a way for me to create 1080p backdrops for music? Meaning, how do these 1080p backdrops come to be to begin with?
With music fanart you often are not going to find anything premade, so you will have to hack together your own. You need a decent art program (any of the free options out there should be sufficient). Then just search google images for pictures of them. You can limit your results by size so that you can weed out small pictures. You can also check out the artist's website or their label for good pictures or press kits as well.
You are also are not likely to find something large enough to do full 1080p fanart. In order to full 1080p you need an image that is at least 1920*1080. For a 720p the image only needs to be 1280*720, which is much easier to find. Fanart is preferable to no fanart, so if all you can get is 720 go with it. What I do then is import the image into your art program, resize the image so that the smaller dimension is the correct length (depends if it is length/width or 1080p/720p) then create a fixed sized selection of the correct dimensions. You can move this around to the perfect spot, then crop and you have a perfect 720/1080 piece of fanart.
What I often like to do, especially if the music is more obscure, is not to actually use a picture of the band. Like, for punk bands often a symbol is more iconic than the actually members of the band. So instead I find a good size picture of their logo, crop it down and delete the background, then paste it into a new canvas and fill in the background with a solid color or gradient. The option is to use a selection of album art as the fanart. Album art is usually square, but if you find a big enough source you can usually cut this down into something interesting. Prog bands tend to have elaborate album art, so I'd imagine this would be the best approach for you.