As for choosing div ID or class, it doesn't really matter as far as positioning is concerned, the thing that DOES matter is whether you intend to use it more than once on the same page.
Take a look at this: http://sonspring.com/journal/hoverbox-image-gallery and check out the example. The bits about the hovering and showing a larger image can be taken out, so that you are left with the images which will display next to each other as long as there is room for them within the width of the div they are placed in, then they will wrap to the next line. The whole thing is a long unordered list, floated left and displayed inline. You can download the html and css for it from that site.
Inger, Norway
My work in progress:
Components for Site Designer and the HTML Editor: https://mock-up.coffeecup.com