I've done a lot of HttpHandlers that generate images. It's usually pretty tedious. When I was working banking, I wrote an example HttpHandler that would take two Check Images (back and front) and composite them into a single image on the server side, then serving up the composite. Usually you're messing around in with MemoryStreams and Images, and then you serialize the result out to the Response.OutputStream, making sure the MIME Types are set appropriately. If you're really clever, you'll remember to do some client-side and appropriate caching, but I rarely see that in the wild.