Troubleshooting
Restarting the game is the best way to be sure that all textures reload. I find there are a number of textures that are cached and will not reload with any number of /reloadui's.
Here are some steps that will often correct problems:
Uninstall DarkUI.
Reload the game completely without DarkUI.
Reinstall DarkUI.
Reload the game completely with DarkUI.