@SBisson here are the steps we discussed. Feel free to modify them, I will updated the task post your comment/feedback.

Steps
a. In image search results, skip images that are hosted on Wikipedia as in many cases they are fair use images.
Example

b. In image search results, First show images from the article which are hosted on Commons, followed by other images from Commons based on the article title.
Example

c. In image search results, show images of 640x640 px. Skip the image from the search results if the image's original size is less than 640x640 px.

@SGautam_WMF looks good

Change 788878 had a related patch set uploaded (by Sbisson; author: Sbisson):

[mediawiki/extensions/Wikistories@master] Show only images from commons with width and height >= 640px

https://gerrit.wikimedia.org/r/788878

Change 788878 merged by jenkins-bot:

[mediawiki/extensions/Wikistories@master] Show only images from commons with width and height >= 640px

https://gerrit.wikimedia.org/r/788878

Change 789822 had a related patch set uploaded (by Sbisson; author: Sbisson):

[mediawiki/extensions/Wikistories@master] Filter images from article based on size

https://gerrit.wikimedia.org/r/789822

Change 789822 merged by jenkins-bot:

[mediawiki/extensions/Wikistories@master] Filter images from article based on size

https://gerrit.wikimedia.org/r/789822

Testing

The images returned are all above 640px x640px.