If you use a background material make sure you have a steamer for fabrics that wrinkle. If you use paper make sure it's not creased or crinkled. Those are the two biggest giveaways that you're not experienced. And it's a major pain to photoshop those things out well, especially if it's got a pattern. It's faster just to be wrinkle free from the start. This is why I lean to knits, velour, fleece, and other non-wrinkly fabric. I never, ever use muslin.
Old world wallpaper... look at curtains or go to the fabric store and find what you need. You don't have to spend a lot on backgrounds. Any fabric can be made to work. $20 worth of PVC pipe and joints can make a stand. But a stand isn't even necessary. I've used chair backs to clip the fabric to, and I'm always using the blinds in my dining room to clip fabric to. You can even use push pins if you have a wall you don't mind putting holes in (a friend of mine has a cork board wall in her studio for this purpose). Another good fabric holder can be a sofa. Some are better suited than others. Also, a tall headboard can work well. There's lots of no cost options if you need to MacGyver something up.