If you want more templates for Google Slides, you can either create your own or find some online.
To create your own templates, start by going to File > New > From template in the Google Slides menu. Then, click the "Custom" template option. From there, you can upload your own images and designs to create a template that's unique to you.
If you'd rather use a premade template, there are a few places you can find them online. A good place to start is with Google's own template gallery, which you can access by going to File > New > From template in the Google Slides menu. You can also find many other great options by searching for "Google Slides templates" in your favorite search engine.