Meh, the flashing-lights-in-games thing is waaaaaay overrated as a public health concern. Most photosensitive (=~'flashing light') epileptics require flashes in the range of ~8-18 Hz (mostly in 12-16 Hz), and even then it almost always takes some time to build up, and even then it's a fraction of epileptics that are susceptable. And flashing lights by themselves don't make non-photosensitive epileptics have seizures (or non-eplieptics). Only about 15% of people epilepsy with are photosensitive. A photosensitive epileptic will know to look away if they see their kind of triggering flash.

By the time you narrow it down to the mere handful of epileptics that will have a seizure from one or two flashes (ever hear anyone complain of a single camera flash and epileptics?), you're in a very rare group. At which point, nothing is safe - I heard of one epileptic who had seizures due to orange circles. Other colour circles were fine, other orange shapes were fine, it was just orange circles (which mean no driving...). Another patient had seizures when ice touched their lips. They do exist, of course, but at that point you're optimising for an incredibly rare user. If you're going to optimise for that, there's plenty of usability optimisations that hit way more people that you should be doing first :)

Source: spent four years doing several EEGs on neuro patients per day, each of which had a 5-minute session with a strobe light at various frequencies. Most of those patients were there for epilepsy or suspicion of epilepsy, but not all, of course. Seeing a photosensitive response at 8Hz was uncommon, but not rare. Some people had some response to single flashes (well, 1Hz) but it never built up to a dangerous level - I never saw someone in danger of having a seizure from 1Hz flashes.

/rant (sorry, nothing personal, I just keep seeing this (largely) urban myth)