They send us a PSD, since they'd already use photoshop to create the look. We then manually convert it into our system.
It sucks because it's definitely going to become a weak point of scaling out our system, but till we hit that weak point, we keep going. We've slowly started to build out the design system just to make our lives simpler, and we imagine outsourcing this task to other people outside our company, which means hopefully once we expose it to users, the interface will be simple enough.
Just wanted to add our perspective of this. I think a lot of people don't realize what you can do by hand. The only reason why I thought of doing this is because of Aardvark.
I happened to have been working for Justin.TV and was lucky enough to record that. Otherwise, I bet I'd have been going down the "build it all first!" route.
All the other videos: http://lanyrd.com/coverage/?domain=justin.tv&page=2&...
One of my clients I do some consultation work for from time to time actually prefer the manual process. It allows them finer grained control to better manage the quality of data/advertisements because the majority of what they do involves graphic art. They have effectively turned manual scaling into a competitive advantage.
I sincerely doubt they will always prefer this route - but at the moment it seems like the best approach (until all their clients are computer savvy and solely work with artists and not try to make a flyer or the like themselves with Microsoft Paint).