Are you thinking of the images of trees included in textures? I had to look around to find them myself. They show up if you browse for images in the texture FeatureManager.
I couldn't find them in the appearance tab of the Task Pane, but once I'd applied texture from the Task Pane, the texture FeatureManager comes up, and "tree" is one of the folders in textures when you browse for "Image file path:". There is probably a more straight forward way to get there but appearances in SolidWorks are something I've never really got sorted out, too many other things to worry about.
Just how tree pictures qualify as textures is something I've never quite figured out either.
Many thanks Erik.