Some folks think that mini's must be mini-ized full size patterns, but my definition is broader. A mini is whatever I say it is!
I do sometimes take full size blocks and shrink them down, but mostly I just start with some fabrics I love and start cutting them up and putting them back together.
A book that I started with was a paperback by Gwen Marston. I found it at the library. She has some good, simple ideas.