I believe Chris Coyier put that period at the end of this post title for a reason:

Putting images on websites is incredibly simple, yes? Actually, yes, it is. You use <img> and link it to a valid source in the src attribute and you’re done. Except that there are (counts fingers) 927 things you could (and some you really should) do that often go overlooked. Let’s see…

He goes on to list 15 bullet points of things to consider. This images situation is actually a microcosm of the web (and all software?) itself: it appears easy/simple at first, but the deeper you go, the more dizzying the depth.