In the example you give, there many be dozens of URNs created by different people that all point to the image as it exists on the slow server. You might also contact the publishers of other URNs that point to the original copy and ask them to include the URL to your copy in their URNs. This situation is common in the publishing world. There are no restrictions. Anyone can be such an authority.
Some people switch providers so they can get free Web space.
Many sites exist only for the Web publishing. The situations with being able to publish URNs may turn out to be similar.