In Wikipedia we add a reference to the facts mentioned in an article. This is best practice in many Wikipedias. The argument for adding references is as applicable for pictures. Our pictures are freely licensed and consequently they are open to abuse by people who “improve” on the original. It is allowed. Many pictures improve as an illustration and this becomes clear only when you compare it with the original.
The original is not on Commons. Many original pictures are kept in museums and archives. Wikipedia will improve not only its references but also its relations with GLAMs when access to the original picture is made easy. To realise this we need to remove all the unnecessary layers between the picture as it is used on a Wiki and the GLAM.
Using images from Commons is something we know how to do well. What we need to do is add enough of the meta-data to provide more information and a link to the original at the GLAM website.
It will make us friends and it will help us clean up our act; we can include the license information. This will get us closer to what the intention of the creative commons license is.