But I've used gallery scripts that allowed for the script to be placed in a html wrap so that it fitted into your page design. Can you do that with wordpress, and if so - how?
Yes.... sorta. Depends on what you're talking about.
If you mean "can you include WordPress into some other sort of existing PHP site", then yes. There's three ways to do this:
1. Include WordPress functionality as a sort of "library" and then roll your own code. In your existing PHP page, add this code:
<?php require('/path/to/wordpress/wp-blog-header.php'); ?>
This makes all the WordPress functionality available to you. Then you can add custom code to run through a Loop and show your Posts and such.
2. Include WordPress as a sort of external call that displays the WordPress stuff, and use a custom theme to make it output the HTML you want it to output. For this, it's very similar to the above:
Then you just have to make WordPress use a theme that does the output you want it to output. You'll likely leave out the head and body and such.
3. Turn your existing HTML site into a custom WordPress theme and switch to using WordPress instead of your existing site. This is the best option, really. WordPress leaves all output more or less up to the theme, so your theme can be anything you like. Custom theming is a bit outside the scope of my explanation, so I suggest reading the documentation:
The problem here is that your question makes an inherent assumption that you may not notice. Unlike packages like Gallery and such, WordPress is more of a full site system. It offers a lot of functionality geared towards management of the site, instead of towards one section of a site (like a photo album would). So while you can use it as a piece of the overall site design, it's simpler in the long run if you take your existing site design and gear it towards WordPress instead. You would want to do much the same thing for any CMS (Content Management System).