WP DESIGN: How can I add multiple images in WP?

Hi, I have a question:

Let’s say I want to change the design in Wordpress, how could I do this? For example, if I use the firebug addon, I see that a particular rectangle has this class: fwidgets. This particular rectangle basically looks like an image, which serves as the header for every page.

Even though I might “hide” the rectangle, I don’t want to change the CSS to merely add a background image. I need to add more than one image, so that by itself is not a viable solution. The question is, how do you ADD images in wordpress?

That is, I want to modify WP files themselves, and add images in the correct file (but which one is that, and how to I do this?). I am trying to avoid using plugings or anything of the sort, since I want to be able to reuse any coding for multiple themes.

I know how to incorporate anything via the “pages” and all, using HTML/CSS. But, actually adding design to the theme itself, I have no clue how.

Found it, add this to child header.php page:

<img src="<?php echo get_stylesheet_directory_uri(); ?>/images/image.jpg" />