You can change left 4 dead 2's main menu background or any source game like this.

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The bink file is a video compressed with RADtools bink video.
The backup is just in case you want to delete the addon, it's faster than deleting the bink files and verifying the game cache.
If you want to do it by yourself, MAKE SURE the video's been rewrapped to .avi, otherwise the bink file will have pure static noise as audio. Use the preview option after ~30 seconds of compression, as it takes a very long time to compress a video.
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