Hi,
AFAIK there is not way to control this.
A solution could be to display first a placeholder image, then load the real images in a background task (see Generating List Item Widgets Asynchronously - #4 by maxrdz )
There is an open bug listview: Have an easy way to get visible items (#4688) · Issues · GNOME / gtk · GitLab for tracking which items are visible, but it’s still “in design”…
If all your rows have the same height, and if you know its value and the number of items, then maybe you can use the scrollbar’s adjustment to guess what’s displayed, and load the corresponding images in priority.