You can merge photos with JointImages.
(Unlimited photos can be merged at once)
Just pick photos you want to merge. Merged result will be appeared right away on the screen.
Adding, deleting and reordering photos can be done in a very easy and intuitive way. Press and hold to edit photos.
Merged photo will be saved in your photo library and you can also share with Email, Twitter, Facebook or Tumblr.
When you save in your photo library, it'll be saved in a best fit size.