A screen saver is nothing but a regular Windows application which typically spans over all of the screens and shows no non-client areas. When it is registered for a use account of for "all users", its behavior should be controlled by these command line parameters:
That's all, all the "manual" you need. Probably, that's why writing screen savers is so popular. :-)
Withing these simple rule, do whatever you want. However, when a mouse or a keyboard is touched, you screen saver is supposed to close.
There is a lot of articles and code samples in different languages on this overly popular topic. You will easily find samples more or less to your liking. But even if you don't read anything and utilize those simple principles I just explained, from scratch, you will be able to create a screen saver at once. All you need is general programming skills and one of available UI libraries of your choice. Using .NET FCL is more than enough.