"I'll be shutting up now" is a little different from "I'll shut up" or "I am shutting up now". They all essentially mean the same thing but "I'll be shutting up now" in this context could suggest that Monica, having wrongly assumed that Bob is horribly unattractive, now feels guilty/stupid for assuming he was unattractive in the first place. So she just announces that she's going to stop talking to prevent herself from saying anything else that will make her feel stupid/embarassed. Another scenario: (I've never watched FRIENDS so I don't know what happened in this scene) but if Monica was saying "for all we know this guy could be horribly..." until Bob shows up at Joey and Monica's table and then Monica says "... horribly attractive" right in front of Bob and Bob heard it, then it could suggest that Monica is feeling embarassed for having said that right in front of Bob so she announces she's going to stop talking, as if to prevent herself from saying anything more embarassing. Actually "I'll shut up" and "I am shutting up now" can be used to express these feelings as well. It all depends on the way you say it. But they do sound a little more awkward than "I'll be shutting up now" or "I'm just gonna shut up now", which sound more natural in these types of situations.

Yes cocoa powder and cinnamon powder do LOOK the same as those found at the top of mocha because they're all brown. I'm pretty sure mocha is usually topped with some cocoa powder or chocolate powder. Cinnamon isn't a common topping for mocha, unless it's a cinnamon-flavoured mocha or some other special flavour that cinnamon would complement.

A photoshoot is a session in which a photographer takes photos of someone (usually a model or someone who just requires photos of themselves)