Hi Elisabeth,
Welcome to the forum. I am not sure what type of materials that Helmi is using - it never occurred to me to ask. She hangs out here periodically, but has had difficulty trying to post in the past. I will definitely pass the question on to her.
I can say that different folks here are using different types of backgrounds. I use cloth from a fabric store - very large bolts of it. It is cheap and I don't care if the pets do their worst on it.

I know others use Muslin or plain old fashioned paper.
James