Thanks for reaching out to us! This is actually a limitation of how our collage maker currently works. You can move the image around and zoom in, however you can’t zoom out. This is something we will improve in a future update to the editor.
What you can do at the moment is resize each cell’s border by dragging it. So you could resize the cells to fit the photos, rather than the photos to fit the cells. Another thing you can try is adjusting the overall proportions of the collage (using the slider on the left). While these solutions may not be ideal, they are a workaround until we allow zooming out.
Regards – The Ribbet Team