My favorite kind of Monsters in anny RPG, Skeletons, manny find them a Cliché but i love them. you can do so much witht hem. have hem as normal skeletons in peasent garbs or ancient armour, corroded weapons or preserved gear. have them as part of some ancient culture. wanna make them a bigger threat? theres plenty of spells in older DnD editions to toughen them up. i personally like whean they can reassemble themselfs. if you dont want them to be meelee focused. give them bows and arrows or javelins. You can also have Non human Skeletons, dwarf.orc or elves or even monster skeletons, like a Skeleton of a Giant or a Dragon or a Hydra or a monster thats an amalgamation of various sources. how about a skeleton with tentacles made from spinal cords.