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.
Check your monitor scaling.
My problem turned out to be this:
It turned out to be different DPI-scaling on the primary and secondary monitor. When the secondary monitor was set to 125% (same as the primary monitor) the icons appeared again.
Answer actually provided by User3163 posting on SuperUser.com