I gave you the link already :
Now, as a second option which can be faster or can bring more results, let's say you want to find a scenery for New Delhi airport. On Google search engine, you can also type :
Indeed, VIDP is the ICAO code of New Delhi International airport.
So if you want to know the ICAO code of, let's say, Glasgow, on Google, you can type :
This will show you EGPF in the first result, and it works 99% of the time.
It is long to explain but very fast and efficient to do.
Hope I am clear enough.