to have whatever suits you best.
Keep your index file and all your html files in the root and you'll be fine - that's what I do as a rule. Then create directories as you need them, but keep it simple - you can create sub-directories inside 'images' as you see fit; I always do this on reasonably large sites, particularly where I'll be doing regular content changes. I keep images in sub-directories according to their type (landscape, people, objects etc.) so I don't have to go trawling through a huge list when I want to add or remove images.
You'll find it far better to run a few main directories with sub-directories, rather than creating a mass of folders in the root. Keep your structure tidy and your future maintenance work will be that much easier. We all think we'll remember things when we're in the white-heat of site creation, but over-complicate your site file structure and three months down the line you'll forget where you put things.