Instagram can be used to host a photo contest of campaign. It is quite simple for you to do through your account page. The use of hashtags is the most important factor when hosting a campaign; it is the way you are going to collect the images which are submitted by your followers, so you can properly categorize them once they are received.
Users will be able to click on a tag. One example is a company hosting a competition for the best shoe design. When posting an image, the contestant simply has to add the #shoe (or other hashtag), and their image will be tagged to that word or phrase. From there, other users can click on the tag, will see the latest submissions and will see the submissions with the most comments.
It is important to create unique hashtags so that your followers know which one to use when posting an image, and so the images they share for the contest will be properly categorized when the judging takes place.