Alright, modding the textures of a model is where a lot of peeps get confused.
Yes, the hand texture is just supposed to be a picture. Because its just a texture, not a model.
First you'll need this...(Jed's HLMV)
http://chumbalum.swissquake.ch/hlmv/
1. First, open your model with the hlmv.
2. Click the "textures" tab on the selection bar.
2. There is a texture selection tab. Click this.
3. Click the texture "handfinal256"
4. Click "import texture" and find the hand texture u DL'd.
5. Click "File" then "save as" and save the model in the name of the weapon u were using with a "v_" in front of it. For instance, if u were changing the hand texture on an mp5 model, you would save it as "v_mp5". Or if you were using a bullpup (aug) you would save it as "v_aug".
6. Place the model into your models folder and enjoy.[/b]
Hope that helps you Pep.
ERROR THAT YOU MAY GET WHEN CHANGEING TEXTURES
A very common error that you can get is "Bmp must be same size as the original" This means that the texture you've selected is not the correct size (Size as in pixels)
For example: I have an M4a1 model with the ORIGINAL texture is 512 x 512.
The texture I've selected is 512 x 510. This will not work, and you will get the error.
The best way to fix this is by editing the size of your texture.
If the texture is too big: I suggest using paint to to slighty shrink the texture manually. This may take a couple of tries, so use a copy of the selected texture.
If the texture is too small: Use photoshop to stretch it out to the correct pixel size.