Here are a few possible sources:
In the Source Engine, the startup_loading.vtf file (Valve Texture Format) is a specific image file used as the very first background you see when a game or mod begins to load. startup-loading.vtf download
Double-check that all steps are accurate. For example, the installation path for Team Fortress 2 might be in the "tf" folder under Steam. Provide exact paths if possible. Here are a few possible sources: In the