what if he says yes?

Considering he has a foot fetish that's probably a bad idea

If this is at work, shouldn't you tell someone? I'm pretty sure that constitutes as harassment.

Definitely sexual harassment if he's using a fetish.

Yeah, he really wouldn't have asked you if he didn't think that. Consider it a compliment. Besides, it's not all that bad. When I was first introduced to a guy in the BDSM-scene who had a huge foot fetish, I thought it was ridiculous. But I soon realised that there is something in having your feet worshipped that is pretty cool and empowering. Embrace it. Try it once. Just once. If you see it's not for you, you can immediately put a stop to it.

I would normally agree, but OP has already said no several times. If you were introduced to the BDSM scene you should know how important it is to make sure all parties are consenting and not pressured into it, especially in those situations. He should stop asking. No means no.

You are completely correct, #43. SSC: Safe, Sane, CONSENSUAL. The three most important rules of BDSM. I stand corrected.

Whether or not OP has great feet is irrelevant. Would you say the same thing if OP's coworker wanted to photograph her great breasts? This is OP's coworker. He shouldn't have even asked once, let alone multiple times. That's super creepy and OP needs to report him.

I'm all for expanding sexual horizons and all that, but there's a time and a place for it, the workplace (well most of them) is not it! It's not a compliment, it's an inexcusable over-stepping of her boundaries :(

I think after the first dozen declines then OP should cease being polite and get more forceful.