Field of view matters, for epilepsythat article mentions '20 candelas per square metre'. I think small gifs are unlikely to give anyone a fit.
The real reason to avoid spacky images is out of respect for people who get seriously bad photosensitive headaches like Archie and possibly Prodigy69, and yourself.
On the other hand, since you're not actually having a fit, you could always just hide the image (Firefox's imagezoom extension is good for that, or there might be one that does image-specific blocking).
(,
Sat 21 Dec 2013, 12:53,
archived)
The real reason to avoid spacky images is out of respect for people who get seriously bad photosensitive headaches like Archie and possibly Prodigy69, and yourself.
On the other hand, since you're not actually having a fit, you could always just hide the image (Firefox's imagezoom extension is good for that, or there might be one that does image-specific blocking).