It would seem a reasonable proposition that there should be a standard set of Blender files that could be downloaded by a user for the purpose of benchmarking a Blender installation. I'm not aware of such a suite of files, but that does not mean that I just don't know were to look. If there is such a suite, where can I download it?
The benchmarking file often used is the 'BMW Benchmark' file by Mike Pan, available on the blender.org site under 'demo files':
There are other files on that page which are sometimes used by developers to test Cycles improvements, called 'Production benchmark'.
If you then want to compare your 'BMW Benchmark' results with other blender users you can use the 'Blender Cycles Benchmark' spreadsheet:
The Blender Artist's thread for that spreadsheet is here, just in case the link gets changed at some point.
The BMW blenchmark's website is this, where you can download the test as an add-on:
Note that benchmark is designed to work on a wide range of hardware, big and small, CPU and GPU, leading to some standarized results. It uses a tile size that is not necessarily the optimal for most modern GPUs.