I just do a research on the relationship between the image title and the search result.
I have two images online, with same keywords but different title.
If I search by "building roof", I can find the first image in the second place of first line in first page.
But when I search by "roof", I can find the second image in the line 4 of first page.
As we know, the image can make more money if it can be found more easy in the search result. So I suggest we can do a test before we give the title to our images. To find a title which can be searched easier.
Hope this can help you.