For example:

Step 1: You resize images to 1280x1024.

Step 2: Then you resize them to 1024x768.

On step 2: you can configure the new name in such a way that in the filename only the desired dimensions change from "1280x1024" to "1024x768".

This would allow you to do a quick find & replace where you've embedded the images after step 1, to switch them to the new dimensions.