the header image in the Twenty Twelve theme is a random image on page load.
As it is random … it’s difficult to put next and forward links
– how can you tell if you started with image 1, 3 or x –
In addition, the header is most likely loaded as a background image so you’d have to do some harder coding to avoid a page reload to change from image 1 to image x
If what you are trying to achieve is to have a slider / featured post panel on the homepage then there are many plugins for this.