Saving changes in theme (multisite)

I'm pretty new to the whole multisite-world so I have a question:

I have uploaded a theme and made some changes to the theme, added some pages, some images, changed some text etc, to make it more simple to get started for the users. How do I save those changes, so that these changes will be by default when a new user register? I simply just want all the changes I've made to be default in the theme. Is there an easy way to do this?

Thanks a lot!