Paper
Try a backdrop made of paper. Photography backdrop paper rolls come in every color imaginable. Look for them in local camera stores. These are normally fairly inexpensive. Hang them on a wall, or place them on a roller system made for paper photography backdrops. A benefit of paper backdrops is that because they are inexpensive, you can buy several in different colors, so that you have multiple options.
Muslin
Muslin is also a material used to make photography backdrops. This light-weight fabric is more expensive than paper, but still affordable. Muslin is typically attached to a backdrop stand. Muslin typically has more dimension than a paper backdrop, because it comes in marbled colors. However, if you want a solid colored backdrop in muslin, it can be difficult to find.
Canvas
Canvas backdrops have long been used in photography. This heavy-weight fabric is attached to backdrop stands or motorized rollers. If you want a large canvas backdrop, it can be expensive. Canvas backdrops are typically painted in widely varying colors. Some people also choose to paint scenes or a landscape. This could be an abstract painting with lots of different colors or a more concrete rendering of a sky with clouds or stars.