Most sizes of beads will work; just keep in mind that the bead hole has to be large enough to fit the cord through. For designs using 0.5mm to 1mm cord, I recommend cloisonné beads 8mm or larger or large-hole sterling silver beads.
For designs with 2mm leather cord, I use sterling silver tube, cylinder and drum beads, glass tile, pony, crow, wood and bone beads that have large holes. Tube beads with drops are great because they easily slide over cord and also allow you to attach a dangle or a charm. Donuts and pendants with bails work great, too.