Flash does not need to draw anything bigger than that. We can use tiles. I am an experienced Flash developer, I think it's not too hard to pull off.
To make it happen we need to see more demand, and somebody to do the other side of the app which isn't UI - wrap the .SWF with a proper installable 'package', and manage the whole image scanning part, then put it in one XML file for the Flash to handle (Flash cannot scan for photo files by itself)