I think this is a great shot as it is. The swans add an element of intrigue to the photo. Without the swans, the image would be less interesting. In a perfect world, there might be a distinguished character, perhaps smoking a pipe while admiring the doors. It might have improved the photo but details like that aren't something one can easily influence. As for depth-of-field, it's perfect as shot. The reason is, the foreground doors that are in focus have already defined that there is a row of interesting, colorful doors, each with a unique pattern. The distant doors do not need to be sharp since we've already surmised that there is a series of cool looking doors. We can tell they're all interesting to some degree, which is all that's needed to communicate the idea. It's like cropping off the top of a subject's head to better frame the face. We know what a head is shaped like so we don't always need to see all of it. We assume the rest of the person's head is there, just as we assume the other doors are equally interesting as the ones in focus. It's a great photo and thanks for sharing it.