I just heard back from the support team at Greatives, the team behind the Reload WordPress Theme. I was having an issue where Masonry galleries created in Visual Composer displayed exactly the same whether I was using “Stamped” or “Masonry” as the display mode.
In the demo they have here, you can see that “Gallery Stamp Masonry” looks very different than Gallery Masonry in that the pictures are all cropped to squares, creating a flush look on the bottom of the gallery.
When I tried this on my site, they still all displayed differently and the result was exactly the same as regular masonry. So, I contacted support and explained my problem.
Their solution? Here it is:
As I see in the related URL you are using images with natural size less than 430×430. You need images with 430×430 at least. Try to use the appropriate sizes and you will get the effect you see on our demo.
So I guess you just need to only use images with both heights and widths larger than 430 pixels. It’s a strange requirement, but there it is!