What app can I use to make a collage like this using an iphone?

I've been trying to do this forever and then I saw it on one of my favorite instagramers pages and decided i should use it to explain it a bit better.

EX: What app can I use to make a collage like this using an iphone

I think that you could use the website Muzy.com, and create a collage. You can choose what layout you want, and add pics and other photographs.

Yeah, you can try Fotor, it's a free online photo editor software.
also have app in appstore.
very easy powerful and free of charge
you can choose photo collage
http://www.fotor.com/features/collage.html
have a try, hope you like it