Standard disclaimer that I'm not an IP attorney. For an official answer to this question please consult one.
To Address @LauraA original question:
Yes, technically under copyright law there is a problem with you using photos of ANYTHING in your work if you didn't take those photos yourself (unless you know that the image or pattern is in the public domain). Be it textured paper, pattern papers, or any kind of artwork that gets collaged into your new image.
Just because you've seen something used in illustrations before does not mean that it's legal. You (probably) don't know if the illustrator actually worked out a licensing deal with the original artist (of the origami paper) if the origami paper is in public domain or if the illustrator is just gambling that the origami pattern artist won't ever notice.
BUT as with all things copyright you need to evaluate whether the infringement in "actionable" or not. I am not against collage art, as I imagine you are using it. In fact I'm a big fan! But one person's "unique and creative collage" is another's "Hey man, you ripped me off!"
Quite well known artists like Richard Prince and Andy Warhol used lots of collaged elements in their work -- and got/get sued all the time!
Sometimes those fundamental infringements are allowed under the "Fair Use Defense" So if you are going to use copyrighted pattered papers in your new work you definitely NEED to understand what you are doing. My own understanding is that infringements like you are describing rely on a legal concept called "Transformative Use".
Transformative Use has become one of the multiple factors evaluated in determining whether an infringement qualifies under the "Fair Use Defense"
Additionally it will depend on how much of any one pattern you use, how you use it, and how many other patterns are included. I personally use the test "If I remove this pattern does the concept of my image fall apart?" Restated, does the viewer's understanding of what I'm trying to communicate in this image rely on the creativity of someone else?
But as you can see none of what I've written here is definitive, and honestly you should talk to a lawyer.
@Chip-Valecek I have looked into Pixabay previously for another forum topic. I'm not saying this is a scam or anything, but sites like this always raise red flags for me. If someone is offering for free what pretty much everyone else is charging for -- be cautious. If you use it for a personal project, actionable infringements are unlikely. If you use it for a project from which you make money and if that project could get really big (i.e. a bestseller) I'd check with an attorney first.
@burvantill I would caution you against that philosophy for scrapbooking paper. I think I understand where it comes from. (And feel free to correct me if I'm wrong in your thinking.) After all scrapbooking paper is SUPPOSED to be collaged right? It's supposed to be cut up and combined with other patterned papers and photos and turned into a cool new piece of artwork!
And you would be right -- with one important distinction. It is supposed to be turned into a cool new piece of PHYSICAL artwork. That is, ONE piece of physical artwork. NOT reproduced over and over again in a book, magazine or any mass produced object. If you want to make a second object that's just like that first object, the scrapbook company expects you to buy another piece of paper. That's how they make money.
@kaitlinmakes I feel confident that one of the things SVS (and the podcast guys) want for their subscribers and students is a clarification of murky topics like this. Unfortunately what you've described is confusing. If you have a moment, could you point to the area of the podcast that left you with the remove 80% (?) impression so that they can further clarify what is meant. I am sure that there are more than a few podcast listeners who would benefit as well!