1.3 MILLION posts?? Way to go, you obviously have a great community there
What would make this a great forum for me, visually, would be to ditch the very large notice completely (welcome and NSFW message) so that you're hit with your random media strip above the fold - ie. some actual photos - followed by your forum content. The thing is, it's so self-explanatory what your forum is about, the welcome stuff could be moved to an about us page, or into the side bar.
I'm not keen on your logo (though concede that 1.3 million posts can't be wrong). Something modern and high impact would be better - I like the use of the aperture/shutter as a logo though, maybe keep that on the left as a logo (as you also use it in the node images) and work on "Photography Forum" text to jazz it up or add a nice header background?
A pet hate of mine with XF is the terrible default avatar for non-gendered members because a ? next to posts just looks odd. I would suggest changing all the default avatars to the same image as your node (the shutter) but greyed out, so in these parts of your forum, you at least get something visual that is "in theme":
I agree that huge notice needs some work and you might want to possibly look at this add on to handle that Notifications
The logo really does need some work it is rather large and not that appealing, I would also try looking at your style as the one your running (as default) is very sort of default XF looking. I like the way you have used the Hot Spots add on that is a great idea for this type of forum (might just borrow that idea). The media gallery does look nice and I was really between in doing this one my site. What I find is that your images then get split between those using the gallery and those just using the attachments option. I hope that in time the gallery that I do have and is not running will be able to combine the two methods into one.