Currently the uhc overlay has a bunch of gold stuff, but it would be nice to use in other gamemodes besides uhc. For example, gamemodes where diamond items are rare and would be nice to see a bit bigger, or other healing items like splash potions/drinkable potions of healing.
This could perhaps be done in a similar manner as the item counter mod, where the user could select what items to highlight. However, I understand if there could be potential crashes if too many items are added to the overlay.