>Ochiba lets you upload ZIP archives of images, but then it just creates a new post for each image.

To clarify: it will post all images in the same thread, by default, but there is a checkbox you can unclick to make it post each in a different thread.

Also: the zip handling is a restricted feature, and I put it in for use of ochiba in "photo album" mode (Gallery has this, for example) and is not generally advised for use in "image board" mode. I think the biggest reason why such a feature would be a bad idea for an open image board is that it opens up an avenue for some serious mischief.

>The mentality of thinking in image sets is more for porn collection

I disagree with this. Take a look through any of wakachan's image boards and anytime someone posted a few images to a thread, they could've been spared some work by being able to upload multiple files in one fell swoop, rather than doing the little submit-wait-hit reply-wait-submit dance (where oops! They forgot to click the "Reply" link and now that post went to another thread).

There are interface issues, though. How you could allow multiple file uploading while still providing a way to specify a comment for each is the most significant that comes to mind, because you still want to encourage the discussion aspect.