literally most things that people write off as just ‘textures’ to use in graphics are stolen & unsourced material created by artists or photographers NOT meant to be used as elements in projects without royalty payments. you can say ‘it’s just random tumblr posts they don’t care’ but you wouldn’t want someone to take your work and edit into their work so they can be praised for their beautiful style and creativity even if they just post it on social media w/o profit, would you?? so maybe if you browse pinterest or google images for pictures without finding the original source, you’re using images that you’re not allowed to use without realizing it.
you see it on here a lot especially in (i won’t link anything but i’m sure you know what i mean) those album track ‘aesthetics’ posts, au ‘aesthetic’ posts (you see these less in kpop, but where people use non-royalty free images to kinda craft a visual au), and even just rather typical graphics that have a lot of ‘texture’ elements. and texture packs too!! that’s often where the problem starts; people just collect images (often literal art), compile them in a folder w/o sources, then insist no one can repost those images w/o crediting the person who compiled them. what???