Trace anything you can view on a computer screen! If you are able to surpass the threshold of screen brightness and paper thickness, then it’s pretty easy to trace right from your screen. Also consider that you can edit images to make them easier to trace (e.g. contrast, saturations, b&w, etc). You can do this on your phone screen or television too for smaller/larger dimensions. It is much better than any print out if your going to paint or draw with it. If you have an LCD be sure to use a soft tip or lighter touch.
Some handy uses: make enlarged or mini versions of your trace limited only by your screen ranges also consider the trace potential for projectors; still-frames from videos/films (you can save w/ “prnt sc”); real-life or natural scenes you photograph, or any other untraceable inspiration; type words and trace to make labels or stencils with any size and font; make neat illustrations for geometric precision or complicated schematic notes; capture transient or temporary images; save on printing or editing.
For standard tracing try using clear glass or plastic as a surface and raise it up to position a light underneath to make it more visible.