Which are all the unlockable bonuses?

I've finished the story mode and collected all the treasures, journal entries, journal notes and optional conversations.

With that I unlocked everything I could see in the Extras > Bonus submenu:

• Add-Ons
  • Skins (Nathan Drake: 12 skins, Samuel Drake: 11 skins, Victor Sullivan: 5 skins, Elena Fisher: 7 skins, Nadine Ross: 4 skins, Rafe Adler 5 skins)
  • Weapons (21 weapons)
  • Render Modes (19 render modes)
  • Game Play Modifiers (10 game play modifiers)
• Character Gallery (59 portraits)
• Concept Art Gallery (23 galleries)

With all this bought, I still have 31 "Unlock Points". Is this normal? I couldn't find any use for those remaining Unlock Points. If there are other unlockables I didn't mention here, where are they?

Solution 1:

Based on the list here, it looks like you have all of the unlockable bonuses.

However, you are able to use UP for multiplayer unlocks. If you have only done single-player, that would explain why you have what seems to be "extra" points.