Needing a simple gallery but can only find overly complicated ones

I am a banner designer, I create animated banners etc. I want to create a portfolio which has categories (which would be 1 category per standard banner size such as 468×60, 120×60 etc)..

I don’t want a light box, and when you mouse over the banners I don’t want anything to happen. I just want them to go side by side then once you can’t get another one next to them, go to the next line and continue. I’d like to be able to list maybe 20 per page and have them ‘best fit’ the page without being a thumbnail or resized at all. Something like bannersmall.com’s portfolio is what I am looking for. If it’s a gallery I need with a few extra plugins then fine, but I just cannot get anything to do what I want even though it seems like a simple request?

Are you aware of a plugin that does this? Bannersmall uses wordpress but cannot find the plugin they use.