http://forums.bistudio.com/showthread.php?156705-drawIcon3D-won-t-display-my-custom-texture
When using drawIcon3D, you can assign a texture to it, you can use (I think most textures) in ArmA3, but if you use a texture from within the mission folder, it will appear blank.
Create a texture
Place it in your mission folder
Use drawIcon3D and apply your texture path into the image parameter
It will appear blank ingame
Confirmed on 0.77.108982
Textures from mission can't be loaded. Only from addons.
Hope it will be changed.
Textures load just fine, follow this guide: http://killzonekid.com/arma-scripting-tutorials-mission-root/