<img src="/image/logo.gif" alt="Logo" />
This method works fine if your application will only EVER exist in the web root. If that works for you, fine, no need to read on.
Those that need their assets to be found wherever their CodeIgniter application happens to sit (root, sub-directory, sub-domain) can use libraries, helpers or add base_url() in front of all references to an asset. This does work but seems a bit overkill for something that can be handled with HTML.
My new evil scheme? Use the lesser-known HTML tag
Now all your relative links will be relative to your base_url. Brilliant!
<img src="images/logo.gif" alt="Logo" />
That will work fine, assuming your images are stored in public_html/images. Use some common sense on that.