before that there is 2 simple rules
1) it shouldn't use skeletons for existed allied races
2) it shouldn't use completely new skeleton such as ethereal for example
mine is amani troll that use trolls skeleton and lightforged undead and new dragonic race that use skeleton of worgen that we will meet them in dragon isle
whats your ideas ?
PS: these rules are blizzard rules for creating new allied races not mine