Willard, The problem is more to do with money than imagination, though somebody with some graphics skill is required to come up with the scheme. The Germans either invite or take up the offer of an artist to design their schemes and paint an aircraft that is due deep strip sometime in the near future as the special. The RAF aircraft that normally gets the anniversary scheme is normally the OC's aircraft and the design is most likely done as an in-house competition within the unit (hence the reason most of them look like they have been designed on back of an envelope). I was involved in the design of a well known special about 8 years ago (My aircraft profile was used by the designer to design the scheme (My brother who was on the squadron at the time) and some of the ideas are on the image below including the final scheme which I produced for the squadron at the same time as the jet was being painted), OC 6 Sqn at the time did very much want the Jaguar to go out of service in style. The OC's aircraft in this case was not used as it was on deployment when the aircraft had to hit the paint shop and the final scheme was done by an artist from a well known car company who partly paid for the paint job.
There are people in the RAF who can do this type thing, as Mr Clave who did the 'Nazi' Typhoon is an ex RAF Bloodhound Technician, like myself.
Bloodhound Mk 2 85 Sqn by WS-Clave on DeviantArt