You can change the layout (grid, irregular...) of images in almost any Posterino document. The initial layout of images right after creating a new document from a template is just a handy start configuration.
The basic layout method: grid, irregular and random:
To change the number of images in your document:
Open the popup and display the layout methods by clicking on the button in the top left.
Skip this step if the layout methods (see screenshot below) are already shown!
Choose a layout method (grid, irregular...) by clicking on a layout method icon: