Thumbnail grid with occasional large image

I'm trying to create a grid of thumbnails and I wanted to add some uniqueness to the design by formatting every *th picture as a larger image. Now, I understand the photo would have to match grid spacing to look right.

But I can't seem to figure out how I could get the thumbnails to fill in the empty spaces created when changing an image size a开发者_开发技巧rbitrarily. Does it lie in css position settings? Do the larger images have to be positioned after the thumbnail-grid is made using absolute positioning?

You can take a look at what I mean here: http://ryandury.com/photos/

Thanks

In the site that you gave as an example, there is a formation of One big picture then 3 rows of 5 smaller pictures and another row below it of 6 small pictures. and it goes on and on. now this is just the formation of the page.

can you please give a better description for that thing you want to do with thumbnails.