WSUS says "updates installed", but not really...

Basically what happens. I generated an image with updates for Windows 7 x64. When I tried to install them on a test Windows 7 installation, it said something along the lines: "Installation completed successfully"
But after checking the list of updates, there are none that have been installed.
What could that be?
Also while we're at it - can I add my own updates (downloaded from Microsoft ofc) to the installer?
But after checking the list of updates, there are none that have been installed.
What could that be?
Also while we're at it - can I add my own updates (downloaded from Microsoft ofc) to the installer?