There is a format button above the camera roll when you access your photos from within Instagram. You can toggle this switch between square and full-size images. Again remember that resolution should be above 150 pixels and below maximum 1920 to show up sharp and clear on Instagram.
What Sells Best On Shutterstock?
Some types of photos that sell best are Portrait Photography, Food Photography, Landscapes (usually with people) and fine art photography (artsy).