I hadn't looked at the original image until Box used it for this gif
In this case you should have imported the original image into sketchup directly and use the draw tools to trace the subject as Box did.
No need for Gimp or Inkscape.
With complex images, Inkscape can be of help as it can convert a raster image into a vector image (there is even better software for that but Inkscape is free).
However, depending on the resulting vector, image you might have to clean it, either in inkscape or SU. I try doing the most I can inside SU as it's where I feel most at home.