I just returned from SciPy2015, and I spoke to several people that are using skimage in their workflow. There are some difficulties in gathering this type of information, among others that a) not everyone is on the list and b) people may be somewhat secretive about their toolchains.
it's true that some companies do not want to communicate about their tools: the testimonies on the scikit-learn webpage is a small fraction of the companies using scikit-learn, that were asked for a testimonial by the dev team. Indeed, most of them refused.
I wonder if a survey on the skimage website would be helpful. I.e., "Using skimage? Please let us know!" with a link to a short survey. What do you think?
It sounds like a great idea! For companies that are not familiar with the scientific Python ecosystem, it is very reassuring to know that other companies are using a package.