You can leave out the pickling spice (or use any combo of cinnamon sticks/cloves/allspice/etc.) that you wish but if you leave all the spices out the flavor is going to be "iffy" and very bland IMO.

As for the boiling vs. steaming? Boiling, sorry, or they can be roasted. It isn't being done just to peel. The beets have to be cooked through, fork tender, fully heated. That takes approx 30 mins as is. It would take a lot longer to do that with steam.

NCHFP recipe calls for just cinnamon sticks and cloves, other recipes include mustard seed, wine, dill, black or white peppercorns, bay leaves, etc. Your choice

http://nchfp.uga.edu/how/can_06/pickled_beets.html

Dave