Since this whole thing is still pretty new, we haven't run into that situation yet. My guess would be that we'd then have the option of voting again to eliminate one or the other, or the option of shooting whichever image we wanted or both, if we so desired. ??
I agree about the tiebreakers vote, because that would only delay things and then shorten the amount of shooting time available. I like Option B the best, as that way people can choose which of the two images they want and can go with that, which will add more interest and variety to the entire venture.
I say we elect 3 regular MacRumours and photography forum members to pick the topic for us over the next 4 months. They can decide amongst themselves, and that just saves us this uninteresting bit where we all vote. They could even announce the topic for all 4 months in advance so that we're not surprised later (if we want it that way).
After 4 months, we elect another 3 people to pick the topic for the next 4 months. There's just too much dead time in between assignments. I'd rather there be less formality. It's just too much. Personally, you can pick whatever topic you want, and I'll still try to shoot it.