Is there a special way in Minecraft to render billboard quads? Like rendering a player tag but instead of text it's a ResourceLocation?

Well, if we are talking about e.g. Health Bars above player/mob, then yes.

 

Example (partial) code:

@SubscribeEvent
public void onRenderWorldLast(RenderWorldLastEvent event)
{		
Minecraft mc = Minecraft.getMinecraft();

EntityLivingBase cameraEntity = mc.renderViewEntity;
Frustrum frustrum = new Frustrum();

double viewX = cameraEntity.lastTickPosX + (cameraEntity.posX - cameraEntity.lastTickPosX) * event.partialTicks;
double viewY = cameraEntity.lastTickPosY + (cameraEntity.posY - cameraEntity.lastTickPosY) * event.partialTicks;
double viewZ = cameraEntity.lastTickPosZ + (cameraEntity.posZ - cameraEntity.lastTickPosZ) * event.partialTicks;
frustrum.setPosition(viewX, viewY, viewZ);

//Here my code that gets entities in world and draws health bar over them.
//It's important for you to check some stuff, if you won't the game will crash/gui will be buggy.
//entity.isInRangeToRender3d
//frustrum.isBoundingBoxInFrustum
//entity.isEntityAlive()

//Rest of code is just a normal OpenGL, drawing figures/images like in GUIScreen (almost).

 

Note: I have no idea if this is your "special" way, it seems simple so i guess it's good.