LIVE COLLAGE. It's a free app, although one can upgrade by paying a small price. I haven't yet upgraded, but I do so love creating the collages! It's especially fun with photos of the great granddaughters!
If you click on one of them, you will have an enlarged image - all the better to see the details!
The photo collage below I did a few years ago using Picasa, which is no longer supported nor can it be used for creating photo collages... Sad to say.