Sets the icon to show the ammo clip, along with SetAmmoBar and SetAmmoBarSize. The filepath is relative to the Menu.rfa's Texture directory, e.g. "Ingame[/Magbar Pistol full 32x64].tga". It specifies the 32 wide by 64 high DDS (not Targa, despite the name) image of the full ammo level on the heads up display (i.e. in the lower right corner of the screen).
See SetHudAmmoType for more explanation, and the HUD Icon Tutorial for related information.
Source and more details