Blender 2.82 Alpha just got UDIM Texture support, and it’s a pretty big deal.
When you unwrap your objects for texturing, you do it in UV space, which is an alternate dimension to XYZ space. Images used are usually square and have a pixel resolution that is a power of 2 because that's easier for a graphics card to calculate. So you’ve got to lay out your unwrapped mesh in this square texture space. To get more resolution in one area of your mesh you scale up its corresponding UV islands to take up more of the space than the areas that need less resolution. This works great!