Use the place command to add the artwork, click the embed button in the control bar, drag the artwork to the swatches panel and you will see a big + cursor appear and release. You will now see it as a preset in that panel. All kinds of photos / pictures can be used as a great source for a preset. You can manipulate the raster and then drag to the panel. Another option would be access the artwork via the CC libraries (found in the window menu) and drag that artwork to the art board and then manipulate it and then drag it into the swatches panel.
With recent versions of the application, you can now use the object menu and pattern and make and you can then manipulate the image in countless ways and see a preview of the end result tile, click save a copy to save your work as a preset. You can make multiple copies of the artwork, distort it, re-color it etc and save all those to the presets panel.
On importing the PNG / JPG etc file via the place command you can distort it / scale it / rotate it but you can also crop it within the application. With the object selected go to the crop button along the control bar and click and reposition the bounding box for the crop and apply. You now may have only part of the photo but hopefully that is more useful with all the extraneous parts gone.
You can also duplicate the object by holding down the alt / option key and dragging the object and then re-work that image such as modifying the color of the selected photo using tools such as Randomino plugin as well as Phantasm as well as Adjust color balance found in the edit menu. This can be repeated numerous times, perhaps re-coloring, perhaps rotating the object and more. For the best results, probably best to do the original source image work in Photoshop or Affinity Photo and then place them into the application.
You can fill a normal path with the presets. Select a normal vector path and go to the panel and select the preset to apply to current path. You can also then transform and modify it via the object menu and transform. Scale and set transform objects to OFF and set transform patterns to ON. Set scale and OK.
You can also use them as strokes and not just as fills with images / pattern swatches. Create a line using the line segment tool in the toolbar / box and set fill to nothing. Set the stroke to the preset via the control bar and set stroke weight and width profile. Use curvature tool in toolbar to extend path. You cannot use them with the brushes though. You can also go to the appearance panel and right side menu and select add new stroke and then add the preset to that as well.
You can fill letters with the preset as well.