Top Apps like InstaSize for iPhone
Use full-size photos in Instagram
InstaSize takes your pictures and resizes them so they match Instagram's image limits.
It is a great app to upload an entire image instead of a cropped section. Many images taken with the built-in Instagram camera are lower quality, but with InstaSize you can use the native resolution.
InstaSize also includes a black and white background before importing them to Instagram where you can apply a filter.
You do not get photo editing capabilities, just a resizing program for the service.