if you put the head texture directly in your customs folder, it will get overwritten when TB updates, you have to click, User CP then click head avatar, and upload your head there, or you can click torishop, then click textures, under "my stuff" and upload your head there.
You don't need to put the texture file in the Custom folder. Doing so is entirely pointless. Upload the 24bit uncompressed .tga file you have, and it should appear. Refer to that topic I linked to for further support.
If your see the text: "Curl error ... aborting" and NO file were downloaded successfully (since Toribash 3.1) , it means that Toribash can't access the internet to download the textures.
A firewall or a router might be blocking it.
More information about this, can be found here.