Theme Sites. These are of course thematic, which will be helpful on what theme you want to use in a page. Scrapbooking is like Wordpress. If you are making a website powered by Wordpress, you will look for nice themes that you can work on instead creating your own. It should be appropriate in the long run as you post and update it. In scrapbooking, templates will stick for a long time after some time of adding all the elements, and it will be the basis of the overall look that you can't change. Photo Sharing Sites. These sites are both theme and group sites at the same time. Photo sharing is mostly their goal, but I have seen scrappers post their layouts or projects. So you will get templates or their ideas as well.
Group Sites or Social Network Sites. There are usually dedicated sites for different groups depending on what they are doing. Social Networks are much broader, but groups within them like scrapmoms, scrapsisters, and so many more usually share their ideas and projects. It is up to you whether you will join any group if you want to get more details and interact with the people within the group, but you will get templates in there.