Upvote:1
Omitting an essential part of the application like a photo will not lead to a refusal (a judgement that you aren't allowed to enter the UK, which will be permanently recorded). The worst-case scenario is that your application will be rejected as invalid. You will have to submit it again, but this has no permanent consequences. Your application fee will be refunded, as well.
However, it may be possible to send the photos separately and have them added to your application. In at least some cases, you can send more documents later to support the application, but I don't know if this would be possible with the photos. Also it may depend on the type of application. I haven't been able to find clear guidance on this.
I suggest contacting VFS, as they may have a good idea of what is possible. Also, given that it was their mistake, perhaps they will put some effort into helping you correct it.