I had been using Windows 8 and TortoiseSVN icons have been displaying properly, but after installing Windows 10 I can no longer see the icons for the files/folder status.
As in current recommended answer mentioned, you need to sort the entries of the overlay identifiers in the registry. I haven't deleted those OneDrive or GoogleDrive entries but renamed all Tortoise Folders by adding 3 spaces to bring them on top. Just restart and even with Tortoise SVN client 1.7.9 you'll see your SVN overlay icons under Windows 10 again.