Obfuscate image source location online
When images are monetised for digital download from a photo library or just need protecting as an obligation to the photographer in a photo contest you need a strategy in place to stop the bad guys getting them easily. Files on a web server are vulnerable to unauthorised download by simple HTTP requests. The dilemma is you can't show them on a webpage without giving away their location in the src property of the HTML img tag.
That's why you need at least two versions, a low rez one to show on the page and a full size original that you hide.
So, the first thing your upload system should do is create thumbnails. You need to resize them. ASP.NET gives you a number of ways to do that but the toolkit uses third party image processing tools.