The bug

There are eleven different sizes of experience orb. All of these sizes are stored in the same texture file. This, however, means that there are five remaining regions in said texture file, which go completely unused.

How to reproduce

Simply extract the texture file from the jar, and note the five last textures. It looks like this:

Expected results

There would be no unused spaces. Either all 16 regions would be used for unique textures which see actual use in-game, or each orb size would have a file for itself.

Actual results

There are still empty regions on the texture file that duplicate the second smallest orb and do nothing.

How to fix

There are three possible fixes for this issue:

1. Five new experience orb sizes could be added, using up all 16 spaces in the texture file.
2. This texture file could be split into 11 individual files, each containing one of the valid, actually used orbs, in a similar way to how 1.5 split terrain.png and items.png and 1.14 split particles.png, kz.png and inventory.png.
3. Five experience orb sizes could be added and the file split into 16 individual files per texture.

For splitting, the texture file minecraft:textures/entity/experience_orb.png would be removed from the game, and a new dedicated directory added for experience orb textures instead: minecraft:textures/experience_orb/experience_orb_[SIZE].png. The contents of this folder would then be stitched into a dedicated texture atlas on startup and when loading resource packs: minecraft:textures/atlas/experience_orb.png-atlas. The splitting of experience orbs into individual files could allow for animated experience orb textures, among other things.