I think we can adapt the ordinary rules and say that if a project hasn't had significant attention on HN before, putting up a Show HN is fine. (Assuming, of course, that the guidelines at https://news.ycombinator.com/showhn.html all apply.) The project itself doesn't have to be new to count as "hacker news". There used to be a used-clothing store where I live called "New To You". :)

The site has been up for about 2 months now. We wanted to polish it up and get a few authors on board before sharing it.

Congrats on that much repeat traffic after only two months. Unless your Alexa is way off.

We did a blog post listing 12 great sites to get free stock photos and it did VERY well. I suspect this is part of the really good Alexa rank.