As stated above, I think it would be interesting if some dragons did a "song" along with their display. Some birds combine a little hopping dance with a song, and generally the longer/more complex the song or string of sounds, the more desirable it is. I think it would add a little variety as opposed to just different varieties of flashing the wings and tails. Especially so if it were a smaller dragon or one with higher-pitched or generally "prettier" sounds.
It also wouldn't be the worst thing in the world if some dragons' displays included some demonstration of their bile attacks, since a strong fire/acid/plasma/etc. ability would indicate they might pass that down to their offspring. Also, it would just look cool.
Third and lastly, maybe there should be skills tied to a dragon's mating displays? They could be tied to stats, hidden dice rolls, skill points, or actual practice, but the result would be that a dragon could "fail" a display and fumble it or do an exceptionally good display. This would take more animation work, but the variety it would add would be interesting. Also, if tied to stats, it'd give other players a sense of whether a particular dragon would produce high-quality offspring.