Peter Kuhn has a long and very detailed blog post on storing images in databases using RIA Services.
Source: Mister Goodcat
In the Silverlight forums people frequently ask for help with storing images in their databases using RIA Services. Even though this looks like a pretty common thing to do, it is far from being straight forward, and searching the web does not seem to produce any good results (or I'm just doing it wrong). So I decided to write this quick walk-through of how to do that. This post describes all steps and possible pitfalls to create a complete application for this from scratch, from the database to the UI.