Without seeing the app in the studio, I have a few guesses as to how it was done (or how I would do it anyways). There's no indication that they're hard-coding anything, which is good. You always want to design things to be relative and/or to re-use controls when possible.
A simple replication of this would involve:
Gallery (with controls)
Collection (columns below)
ID (always helpful to disambiguate rows)
A single Gallery can span the majority of the screen. If you reduce the Template Padding and Template Size to 0, then you effectively have a mechanism to repeat a control as many times as needed. You can then make the X,Y of the Image (per row of collection), relative to the Height/Width of the Gallery (not the Gallery Template), and then any number of Images will effectively scatter across that range.
The tricky part is how to handle overlaps, and the relative positioning. Hence the variables, for positioning at least. This way, you can derive the max/min of your data set (per axis), to help show the numeric scale. Then positioning the record relative to the max/min, and relative to the Gallery width/height, will position it appropriately.
Let me know if this helps. I can whip up a crude sample, if needed.