Installing Sprites/others on Counter-Strike 1.6 with Steam. If you have
  downloaded 1.6 via Steam i'm sure you have being wondering how you change
  skins, sounds, sprites. When you go to the cstrike folder that steam uses:
  C:\Program Files\Steam\SteamApps\<user@mail.com>\counter-strike\cstrike
  You will notice that it is rather bare and has no folders like the old 1.5 structure
  i.e. Models, Sprites, Sounds.

  The picture below shows my directory which has folders which I have created. If
  you create the folders and put the custom maps, sprites, models you want then
  steam will use them.

  1. MAPS FOLDER - Place any custom map files .bsp into this folder, steam will use
       the maps. This folder will be made by steam if you chose to add custom maps
       from cs 1.5 to 1.6 when steam converted it.

   2. MODELS FOLDER - Place custom models in this folder, the old 1.5 way with
       some models renaming the v_m4a1_r.mdl to v_m4a1.mdl way doesn't seem
       to work anymore, I think valve have moved back to the old model way of just
       mirroring.  I am using the v_m4a1.mdl file instead of renaming the _r.mdl and
       it works fine.  (Im using m4a1 models as examples of model structure). If you
       want to change the player models i'm guessing you would make a folder within
       the models folder called PLAYER then inside that folder several sub folders for
       each player:
       arctic
       gign
       gsg9
       guerilla
       leet
       sas
       terror
       urban
       vip
       So if you wanted to install a new arctic skin you would place the model file in:
       cstrike\models\player\arctic

   3. SPRITES FOLDER - Place custom sprites in this folder and they will be used, I
        placed:
        weapon_aug.txt
        weapon_sg552.txt
        selfmade.spr
        Steam used these and I had my crosshair on the sig and aug in zoomed mode.

   4. SOUNDS FOLDER - Place all custom sounds in here, these will be used in with
       steam, steam also downloads to this directory if a server has sounds that you
       don't.

  Hope It helps - Battlegod58