I din't recall moments of it in the film but in the early teaser there seemed to be a good deal of chromatic abberation on the older Flynn when you see him in close-ups. maybe touches like that could be interesting...?
ie:
.jpg/220px-Chromatic_aberration_(comparison).jpg)
I can't remember offhand if the digital world in the first film was entirely computer styled but remember that legacy had skies and rocky ground and stuff that you might be able to emulate also.
I really need to get my dvd of tron back and watch it for ideas...