You can use any Keyboard, Mouse, Display.
That is the whole purpose of the Mac Mini, BYODKM, which stands for bring your own display, keyboard and mouse, its another one of those stupid computer geek acronyms like WYSIWIG (What you see is what you get) and GNU (GNU's not Unix).
Back to they keyboard, as I said any keyboard will work but you may need to remap a couple of the keys as Mac keyboards are different from PC keyboards.
Nick.