Well, on putting textures in your custom folder, isn't it just due to tb updating a lot faster? So if you have no internet, you'd be fine. It'd just be erased upon connection to the tb server.
Unchecking the RLE compression is a major thing to note. I'm surprised that it took three replies before slip mentioned it. :O
I'd recommend just DL'ing GIMP to save as .tga
If you are making textures, you shouldn't be using MSpaint anyway.
GIMP is also free. There really shouldn't be any reason why you shouldn't download it.
The head also has to have square dimensions. If I remember correctly, having it in 128x129 would be enough for it not to show up. (I have mistyped my dimensions a few times before)
But yeah, the new customs folder is pretty essential.
The parts:
head = head.tga
right biceps = r_biceps.tga
right forearms = r_triceps.tga (seems like someone slept during anatomy class :P)
and r_thigh.tga and r_leg.tga
just replace r with l for different sides. note that the arms are plural while the rest is singular.
go through people's customs folder or search for a full list.
I KNOW there are several threads out there with the proper names.