Things You'll Need
Instructions
Setup
Close the Steam application. Right click on the Steam icon in the Windows System Tray and select "Exit." You cannot successfully alter games associated with Steam while it is running.
Download the latest version of GCFScape from the website Nem's Tools. Click "GCFScape" in the main navigation menu and then click "Download." Click the "Installer" link to initiate the download.
Double-click the gfscape.exe file to launch the installation menu. Accept the agreement and allow the application to install "GFScape" to your computer.
Obtain the VTF Plug-In for Photoshop from the same website. Select "Miscellaneous" from the main navigation menu and click "PS VTF Plug-In." Click the "Archive" link to get the file.
Use your preferred file compression utility to extract the "psvtfplugin" file and open the resulting directory. Click and drag (or copy and paste) the "VTFLib.dll" file into the "Program Files\Adobe\Photoshop" directory. Transfer the "VTF.8bi" file to the "Program Files\Adobe\Photoshop\Plug-Ins\File Formats\" directory.
Browse to the "C:\Program Files\Steam\SteamApps" directory on your computer. Double-click the file named "team fortress 2 materials.gcf." A GCFScape menu will appear, showing the contents of the GCF file.
Double-click the "tf" folder to open it. Open the "materials" folder and double-click "Models."
Creating a Custom Skin
Open the "player" folder and double-click one of the character class-specific folders contained within (for example, "spy") to create a custom character skin. Alternatively, if you want to skin a weapon, double-click the "weapons" folder and open any of the folders beginning with the letter V and an underscore.
Right-click on a VTF file (for example, "spy_head_red.vtf") and select "Extract." Select a destination folder on your computer for extraction (any folder will suffice) and click "OK."
Launch Adobe Photoshop. Select "File" and click "Open." Browse to the location of the extracted VTF file and click "Open." Using the program's tools and effects, customize the skin however you wish.
Click "File" and choose "Save" when you're ready to load your custom skin into "TF2." Ensure that you preserve the original file name and extension.
Importing Custom Skins
Right-click your Desktop, select "New" and click "Folder." Name it "materials." Open this new folder and create another folder called "models."
Open the "models" folder and create an additional folder. Depending on the nature of your custom skin, name the folder "weapons" or "players."
Add a new folder within "weapons," if you made a custom weapon skin, and rename it to match the "v_" folder from which you extracted the original weapon VTF file. If you created a character skin, create a folder within "players" and assign it a name that matches the character class folder containing the extracted character VTF file (for example, "scout").
Click and drag (or copy and paste) your custom VTF file into the last subfolder you created. Browse to the "C:\Program Files\Steam\SteamApps\" directory. Open the folder named after your own Steam username.
Double-click the "team fortress 2" folder and open the "tf" directory inside. Place the root "materials" folder you created within this directory, and your custom skin will appear in "TF2" when you play.