A basic concept of how to implement a custom tip in VRTK

CustomTip.cs

using UnityEngine;
using System.Collections;
using VRTK;

public class CustomTip : MonoBehaviour {

    private VRTK_WorldPointer pointer;
    private GameObject cubeCursor;
    private GameObject capsuleCursor;
    private MeshRenderer sphereCursor;

    void Start()
    {
        pointer = transform.GetComponentInParent<VRTK_WorldPointer>();
        pointer.DestinationMarkerEnter += Pointer_DestinationMarkerEnter;
        pointer.DestinationMarkerExit += Pointer_DestinationMarkerExit;

        cubeCursor = transform.FindChild("Cube").gameObject;
        capsuleCursor = transform.FindChild("Capsule").gameObject;
        sphereCursor = GetComponent<MeshRenderer>();
    }

    private void Pointer_DestinationMarkerExit(object sender, DestinationMarkerEventArgs e)
    {
        cubeCursor.SetActive(false);
        capsuleCursor.SetActive(false);
        sphereCursor.enabled = true;
    }

    private void Pointer_DestinationMarkerEnter(object sender, DestinationMarkerEventArgs e)
    {
        switch(e.target.tag)
        {
            case "Cube":
                sphereCursor.enabled = false;
                capsuleCursor.SetActive(false);
                cubeCursor.SetActive(true);
                break;
            case "Capsule":
                sphereCursor.enabled = false;
                cubeCursor.SetActive(false);
                capsuleCursor.SetActive(true);
                break;
            default:
                cubeCursor.SetActive(false);
                capsuleCursor.SetActive(false);
                sphereCursor.enabled = true;
                break;
        }
    }
}