There's isn't a lot of flexibility there. There is also a feature that lets you create videos with photos.
You point the app to your photo roll, select the photos you want to use, and the rest is pretty obvious, with controls along the bottom of the screen. I have used the app on several of my pictures, and find it straightforward. Your finished collage can be shared with the various social networks, emailed, or saved to your camera roll. You can also select background colors, frames, text, and stickers. The layouts that appear depend upon how many photos you have. You can select the aspect ratio for the photos, and choose from more than 300 layouts. Photo Grid is a free (ad supported) app with lots of options for creating collages, as well as video slide shows accompanied by music.
