The problem is partly related to the internal mechanics of the Godot Engine. It seems that they use a static sized queue for messages and adding new GUI elements is handled with messages. There does not appear to be a way to change this size after a game has been compiled. Also, Strive sets up all the picture GUI elements at the same time, so with a large number of pictures that overwhelms the engine. It should be possible to add code which creates the GUI over a period of time rather than all at once, but I haven't confirmed the results yet.
It's hard to know the exact limit of the number of pictures Strive can currently handle, but I would recommend reducing the number of pictures until it works. Though I would appreciate knowing how many pictures you have, as a reference for my tests. On Windows you can get from the properties of top folder.