Even though you can see a fantastic tiled/wrapped image you still have to sample colours using CTL from the actual image, which of course you can't really tell where it is. I understand the possible need for this as the tile is simply a simulation of what the texture tiled would look like so maybe a way to highlight the actual image might be a solution. 

Reproducible: Always

Steps to Reproduce:
1. turn on wrap mode
2. hold CTRL and try and sample from outside the image space (from the tile)
3.YOu should only get black
Actual Results:  
You get black

Expected Results:  
You sample the colour you wanted from the screen