Adding functions similar to uncrate.com

I have a client who wants certain functionalities that are shown on uncrate.com

Namely the ability for the user to switch the index display from full(posts) list(excerpts) and grid(thumbnails).

I am aware there is a plugin or hack somwhere that allows a user to select themes, and this would be one way of doing it – but is there a way to do it within the one theme?

Also for the grid option – I’ve used alakhnors post thumbs in the past, but the new version was seriously slowing the website I used it on. Is there a better solution for dynamically creating a thumbnail grid from each post?

Thanks

Dan