Your board can be a lot more than just switches! You can add RGB LEDs, rotary encoders, sliders, a buzzer, joysticks, and an OLED screen.
A lot of popular keyboards are open source, so you can look at them for inspiration.
#Finding symbols and footprints
A lot of these can already be found in the default KiCAD libraries or marbastlib, so you should look in these places first.
If you can't find what you are searching for in the above mentioned sources, you should search on SnapEDA or Component Search Engine.
#Finding 3D models
You should search on GrabCAD and sort by most popular, and you will most likely find the model that you are looking for.