UPDATED:
Starting with version 15.1, the HtmlEditor extension has a similar functionality that allows accomplishing a similar task with less effort and does not require so much extra code. See the Image Upload Processing demo to learn more about this new functionality.
The example shows how to save an image uploaded via UploadControl to a database. The main idea is to get an uploaded file using the UploadControlExtension.GetUploadedFiles method in the UploadCallbackRouteValues Action and execute custom SaveImage code.
