multiple picture for background

Hi,

i have 2 questions of html and css. I am still relatively new, so sorry if the questions doesn’t make sense or too trivial:

– my landing page consist of 2 big picture that will bring the readers to 2 different areas. i put the picture, and use <center> and put link to the picture. but the problem is that even the empty area next to the picture also become clickable. any html code i should use to limit the link to only the picture?
– how can i create background that will be static? meaning that no matter in any screen size, it will be static and not scrollable? i was thinking of putting 4 different picture and put their alignment to upperright, upperleft, lowerright and lowerleft. is this the correct method?

Thanks ??