CreatureDisplayID

Display IDs are models with optionally a texture applied, most of them can be found in CreatureDisplayInfo.db2

Example
Shows a murloc on the frame in the Character Pane, which has model   and texture /run CharacterModelFrame:SetDisplayInfo(31)

Finding IDs
Display IDs:
 * Returned from various in-game APIs.
 * Viewable in-game with addons like rIngameModelViewer which use

By NPC ID:
 * They can be parsed from CreatureCache.wdb which can optionally be populated by tooltip scanning for  hyperlinks.
 * https://www.wowhead.com/npcs - Datamined list of NPCs, available in the html page source by looking for "displayId"
 * https://wow.tools/db/creatures.php - Datamined list of NPCs.