A few points I have in mind for further development of the site

Of course, to actually get to do them, I'll have to receive at least moderate interest for it in its first basic form, otherwise I can't really see me putting a good chunk of further work into it.
Anyway, the main ideas are:

1. The most important one is personalizing of the looks.

1.1. Clock view, that is without the Web elements like menu, menu button and notes. Also, the clock image in this view must be set up automatically so that it makes best use of the screen.
     Probably as a variant of this, there should be a view that doesn't feature the image of the clock object, just the hands and the face with the cities and hour numbers. This way, the frame of the device acts like the clock object.

1.2. Latin hour numbers.

1.3. More color schemes. As a minimum, one with dark cities and hours on a light face. Ideally it should be user-configurable but that's not that easy.

1.4. Probably the most challenging and most substantial: a variety of clock designs. As a minimum, the user should be able to choose from something like 20 - 30 predefined designs. Most if not all of them should come in at least 2 color schemes, light and dark.
     Again, ideally the user should be able to enter his or her own clock design. And again, that's not very easy. I haven't thought about it in detail but I guess it won't be done for the world clock.

1.5. An interesting possibility would be to have a configurable clock without the world time part. Just a simple clock, but one for which the user can choose the design like above. Kind of like a software-configurable pocket watch.
     Without the cities on the face, creating a new design is much easier, so one could envision a feature here that lets the users supply their own design. At least to some extent.

2. As a means of helping the user to quickly find the desired city, it would probably be useful if the face was divided into a few big zones, indicated by the flags of the main countries of each one. I'm thinking probably 4 zones: US, Europe, Russia and the rest of the world (there would naturally be gaps between these 3 that would create a 4th one).
   In my taste it would make the look a little less classic, but it could improve functionality, at least for a user who's not yet accustomed to this kind of world clock. After they gain experience, they can remove the flags (which are of course optional).

3. It could be useful to have a variant in which the time is taken from a real time server, not from the system. Then again, the user can synchronize the system clock from a true server. Maybe if they're on a system that doesn't offer this possibility.