How do you place an image on an object so that the object size is based on pixels per unit and image size?

So, I figured out how to do some of this.

One thing I did do was snag a plugin to deal with the runtime browse to file that was super easy to setup and use: https://assetstore.unity.com/packages/tools/gui/file-browser-windows-macos-98716

Created UI->RawImage object.

Add "Box Collider" component to RawImage you just made.

Create MapManager script, attach to RawImage object.

Create UI->button.

Add onclick slot to button.

Drag RawImage object to the onclick slot you just made.

Select LoadFile() for OnClick function.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using Crosstales.FB; // see LoadFile() function for more details on this plugin
  
 public class MapManager : MonoBehaviour {
  
     GameObject mapBoard; // GameObject->UI->RawImage, child of "Canvas"
     BoxCollider boardCollider; // added box collider to ^^RawImage so objects wouldn't fall through if placed on them
     float currentImageX; // storing height
     float currentImageY; // storing width
     RawImage rawImageMap; // Raw Image attached to mapBoard
     WWW currentImageSelected; // image user selected in dialog
  
     // Use this for initialization
     void Start () {
         mapBoard = gameObject;
         rawImageMap = mapBoard.GetComponent<RawImage>();
         boardCollider = GetComponent<BoxCollider>();
     }
  
     // resize the collider to match new size of the image
     void SetColliderSize(float x, float y, float z)
     {
         boardCollider.size = new Vector3(x, y, z);
     }
  
     // load file via dialog at runtime
     public void LoadFile()
     {
         /* open dialog and let user select file at runtime
         * Can do this with plugin from:
         * https://assetstore.unity.com/packages/tools/gui/file-browser-windows-macos-98716
         */
         string extensions = ""; // filter *.jpg and *.png?
         string path = FileBrowser.OpenSingleFile("Open File", "", extensions);
         // end dialog code
  
         Debug.Log("Selected file: " + path);
  
         currentImageSelected = new WWW("file:///"+path);
  
         rawImageMap.texture = currentImageSelected.texture;
         rawImageMap.SetNativeSize();
  
         Debug.Log("Image Name=" + rawImageMap.name);
         Debug.Log("A X=" + rawImageMap.texture.height);
         Debug.Log("A Y=" + rawImageMap.texture.width);
  
         currentImageX = rawImageMap.texture.width;
         currentImageY = rawImageMap.texture.height;
         SetColliderSize(currentImageX, currentImageY, 1.0f);
  
     }
 }
  

With that you can "Play" and it will show a button, you click, browse to a local file anywhere on your system and select. The RawImage object will grow to accommodate the image height/width as well as the collider around it.