The range for wombats does not extend to the west Kimberley region at all. That said, this is a rather remote region, and not the kind of country one treks over by foot. I do most of my bushwalking at night, because the day temperatures are quite high, and so is the humidity.
Large older wombats don't match what I saw, and the prints are clearly elongated, rather than wide, like in your photo. The toes are longer, though the claws are a good match. Perhaps this critter is a large burrowing animal, rather than a tree climber. Not many larger trees around here, except for the mahogany trees planted on our block.
It would be great to have found a new species, but I'm thinking I'll have to do a lot more night walking, to have any hope of sighting this creature again. There are feral dogs, donkeys, and rather large scrub bulls in this region, so I have to take my dog walking with me for protection, which is not conducive to spotting wildlife.