Why am I collecting visual data?

At the moment I'm unconvinced of the value of carrying out visual data collection.  To be honest, I've never been totally sold on the idea, but then I've never tried my hand at this kind of thing therefore maybe that's to be expected. When I'm already hard pushed to submit my dissertation by the 'early' August deadline that I've set, this would seem to be an exercise that will be time consuming beyond the merit that I can see it providing.

As a newcomer to visual research I'll obviously need to do some research into how it should be done. And having never carried out this visual analysis, there's no guarantee that I'll be any good at it. Even if it does prove to be something I am able to do effectively, how much value would a handful of images add to the project? This is all over-and-above determining what I data I'm trying to collect and that actually collecting it.

Might I not have sufficient data with the seven interviews followed by observation? Although this is something that Sian is keen for me to try (on the basis that she thinks I'd be good at it)..

So I have two key questions/concerns (over and above whether I'll be any good at visual analysis): 

1. Even if it produces meaningful data)Will the likely results of the visual exercise justify the amount of time it will take to carry out the exercise (particularly considering the tight time schedule I'm on)? Would it not be pragmatic to dispense with this exercise to enable more time to be spent on analysis and writing up (a task that the visual exercise would in itself increase)?
2. If it transpires that the exercise doesn't produce any meaningful data is it OK to ignore it? Can I discreetly dispense with it or there is a requirement still to discuss what I did and what came out of it (or more pertinently, what didn't)? And if the exercise has 'failed', will that impact on the overall strength of my dissertation?