Here is a great writeup discussing Sputnik Planum on Pluto, and the apparent glacial flows in the region. The author, Orkan Umurhan, mentions several times the similarity of SP and hot wax. I don't think I fully grasped the similarity and admittedly, I didn't seek any photos to further educate myself to his analogy.
Well, today came and I had a project which required pouring blocks of hot wax. While they were cooling, a very familiar scene appeared.
This has a remarkably similar appearance. For comparison, I've linked my version of the Pluto global MVIC image, which makes the convective cells more visible. What seems most interesting to me is for the darker regions to exist in the wax, liquid has to be present very near the surface. Very similarly dark regions are present on Sputnik Planum as well. The linked article above suggests that the 'liquids' present here are quite viscous. While very different substances are at play on Pluto, this simulated Sputnik Planum would suggest much less viscous liquid is necessary for the darker regions to be present. Once the surface cools enough, it becomes a much more homogenous surface in appearance and I think we see that on Sputnik Planum as well. Nonetheless, Orkan Umurhan has dedicated himself to the subject and I respectfully bow out to his much better expertise on the matter.