Are custom content types only for custom types of posts or can it be anything?

With regards to the new custom content types in 3.0, most tutorials I read refer to and develop them as ‘custom post types’.

So I’m wondering, are the custom content types limited just custom types of posts?

I’m putting together a custom image gallery type thing for a client. And I think it would be best to add a custom content type of ‘images’ that my client could easily add or remove images at will. There are several pieces of meta data that need to go with the images so thats why it seem like this is a good approach.

All the images (in the gallery) appear just on the homepage of the blog. They are not going to be viewed individually. So on a single page I need to query all the available ‘images’ and then display them.

So anyways, can this be done with custom content types? And again, are custom content types really just custom post types? Is this the approach others would take?