I've also made an example 8192x8192 image available for test purposes. It is based on the Carina Nebula shot from Hubble.
For comparison, here's the previous method of speed measurement, heavily influenced by the PNG decoder:
$ time etcpak.exe 8192.pngAnd here's the new benchmark mode:
$ etcpak.exe 8192.png -b
Image load time: 1330.949 ms
Mean compression time for 50 runs: 631.308 ms