Gallery flags

I am using the WP gallery function (no plugins).
On mouseover an image, there appears a very large black flag with the image description.
This is good idea but the flag is much too large; it would be better about half the size. With a small image it might cover the image so it could not be clicked.
Also, if it can be useful in a gallery, it should also be used for all images.
Not an urgent problem but worth addressing in the next revision.