1) Locate the Aperture Package (by default this is in your Applications Folder.)

2) Control-click on the package and select SHOW PACKAGE CONTENTS. Then open the Folder called CONTENTS and navigate to RESOURCES/WEB THEMES.

3) Select one of the existing themes to use as a model. For the purpose of this posting, go to ART COLLECTION by double-clicking and opening that Folder. Make a duplicate of that Folder so you don't mess up the default choices.

4) Inside your duplicated ART COLLECTION you will see another Folder called English.lproj. Open that Folder by double clicking it.

5) Modify the HTML pages you see here as you see fit. As I said earlier, you will need to know HTML and/or CSS.

6) After making basic HTML and CSS changes, you may want to go further and customize the images that go with the theme. They are found in the assets:img Folder. Here you'll find all of the images that are used as navigation icons. You can edit these in a graphics program like Photoshop or you can replace them with your own.

7) If you want Aperture to display an icon that represents your custom theme, you'll have to create it yourself. It needs to 90x105 pixels and saved with the name THUMBNAIL.TIFF. Place this file inside your new theme folder.

8) Once you've made your modifications, be sure to save them in the appropriate places and then drag the new or modified theme into the WebThemes folder inside the Aperture Package. You won't see the theme until you quit and re-start Aperture.

9) Save your theme in a backup location, since installation of Aperture updates may overwrite your WebThemes folder, rendering all your customization worthless.

This is in no way meant to be a tutorial or detailed article on how to customize Aperture web themes. Instead, it's designed to get you thinking, experimenting and playing with Aperture's web themes in a way that will hopefully lead you to your own discoveries on how to customize Aperture.