How to explain to a customer that their artwork resolution is insufficient.

Customers typically have absolutely no knowledge regarding artwork resolution; however, we need to put ourselves in their shoes.
All the customer really wants to know is: which artwork option will look the best? Here is an example of how I explain this to customers:

I completely understand. Regarding this matter, I will consult with our designer. He frequently assists our customers in enhancing image resolution; if he is able to improve it, then your designer won't need to duplicate the work. However, if the resolution of the original textures is inherently low, our designer will replace them with high-definition alternatives. Since our designer was not involved in the initial design phase, we would have to select replacement images that are closely similar to the originals. Would that be acceptable to you?