I found a nice app called PicFrame.
You can make a photo collage by combining multiple photos with this app.
As it's name suggests, it is not that you can make a completely free form layout photo collage, but you can only put photos in predetermined rectangular frames.
You can move drag and move borders to resize individual photo areas.
You can change the size, round corners, rotate and mirror photo images.
In "Style" menu you can select color or pattern, and width of frame. But you can't change the color of patterns.
Completed photo collage can be saved in CameraRoll, or shared on Facebook, Flickr, Twitter and Tumblr.
There's Mac version of this app too, but basic function is same. The only difference, at least I could notice, is Mac version has more choices of frame aspects.
Here I made some examples. Hope you'll enjoy and give it a try, it's fun :)
