On server part ( I mean database or xml ) you can change the shear of npc / monster. Size of monster / npc you can change in editor ( need to edit model of monster, model is in *.ukx package ), next you can set translation of model.
P.S In Lineage you can view LineageMonster.ol_mahum_warrior_50_bi on npcgrp.dat
_50bi => size of monster is 1.5 ( 1 = default size, 1.5 = increased by half ). bi - big, sm - small.
Another example:
LineageMonster.ol_mahum_40_sm => size = 0.4 ( ~ half at original size of npc / monster ), sm - small.
If you have npc / mob with style ( dat example )
25272 LineageMonster.ol_mahum_champion_50_bi LineageMonsters.ol_mahum_champion_m00
25272- ID of monster / npc
LineageMonster.ol_mahum_champion_50_bi - script of npc / mob
LineageMonsters.ol_mahum_champion_m00 - package with model
If you change LineageMonster.ol_mahum_champion_50bi to LineageMonster.ol_mahum_40sm then your monster / npc will have 0.4 size at original. You can use this for all another monsters / npc, but you need to know what script use animations name ( wait, atk, walk, run ) and your npc can use ( wait_1H and etc... ) => your npc will not have anims. Try. :)