Health (Hearts), Hunger (Drumsticks), Air (Air bubbles), Armor (Iron Chestplate), Mount Hud (Saddle), Experience Bar, Mount Charge (XP Bar but blue and yellow), Camel Recharge (Dark purple bar), Hotbar attack indicator, Crosshair Attack indicator. and Player connection indicators.
Where can I get the HUD textures?
Right here! For your convenience, I also added the pre-1.20.2 textures, so your pack can support both versions. Remember to delete the textures you don't need in /assets/minecraft/textures/gui/sprites.
[OUTDATED] Where can I get an icons.png file?
Here's one only containing what you need! The vanilla one is full of useless stuff that doesn't get ever used.