Go and visit some friends with loaders, or head over to an implement dealer and pick up some literature. The internet has unlimited information.
Often times farm tractor loaders have a different bucket design/shape than a construction machine as well as being lighter in weight for the same size.
While you can dig with a farm tractor, it is designed more for moving material than rough digging or handling rock and concrete all day long. Not that you can't do rough work with a farm loader, but it will generally break sooner than a construction machine.
With all that in mind, take the best design that you like and scale it to your machine. Of course the mounting will have to be designed around your machine specifically. Usually the width on a general purpose bucket will be a couple of inches wider then your machine. A bucket for handling wood chips, or snow is usually larger and wider for handing lighter materials, but can overload a machine handling gravel, etc..
Most fab shops can shear/cut the steel and also bend it based on a set of sketches. As a bonus, they probably have already built one or two previously, and can make adjustment or suggestions to potential issues. Bring it all home and spend a day or two welding and painting. They probably either stock or can get a cold rolled cutting edge easily.
Many folks use the Google sketch program for designs, although I have not used it having access to AutoCAD myself.