Sorry, I unintentionally created a new thread on a similar topic: pandoc logo - Google Groups. Any further discussion should goes here.
Over there I draft a design of pandoc logo by playing on the symmetry between P and d. One expression of that idea is an axe looks like P and the same thing rotated looks like d. The reason an axe is used is because this kind of echo pandoc being like a Swiss army knife, where an axe is like that on steroid. A proper design of that axe should resemble the letter P and d better.
Another way the pd trick would work is to partially overlap the circle while using negative space.
If anyone think that’s a good idea, I could create a better draft of the idea.
As to where the logo is needed:
One consideration on designing the logo might follow the \LaTeX example which is text only, because pandoc is primarily for processing texts. To push this idea further, we might even be constructing this logo by math so that together with a macro, using something like \pandoc in markdown will output a proper pandoc “logo” in any output formats.
Another point is to make sure the logo looks great both when it is very tiny (16x16??) and very big.