Minecraft Left2Die has a custom texture pack that is loaded automatically when you log into the server. The first time you join, you should be prompted whether or not you would like to use this texture pack. Should you choose the wrong option, follow these instructions to change it.
- Select the server from your server list.
- Click the "Edit" button
- Toggle the "Server Resource Packs" button to either "Enabled" or "Disabled".
- Click "Done".
- Login to L2D. The server resource pack should now load automatically.