My husband and I have about 200 photos from the 3 ten day long visits we have had together...I could narrow them down and probably should...
What is a good amount of pictures to send in?
It depends on your situation. Applicants from America and other 'first-world' countries need less evidence than people from 'third-world' countires. Someone who is very similar to his/her partner needs less evidence than someone who is very different. Relationships that are unusual in any way need more evidence.
So if you and your husband have only been together for 30 days, I would suggest you need to send more photos than a couple who has been together longer. If you have other red flags - such as a big age difference - or very little proof of contact other than these visits, you should also send in more.
Lots of people have sent in 200 photos or more. You could cut the number by not sending many photos of the same event, though. For example, if you have 10 photos of the two of you at Niagara Falls, just send one or two.