Thanks to the help from a few folks I have put together a description of the Icon Keys on the Extra Keys page, in order from left to right - please let me know if there are any errors or if you have the Unicode codes for the missing items:
Icons Row 1 (Unicode in parentheses):
1. ← Backspace
2. ← Backspace
3. ⇥ Tab
4. ⭾Back and Front Tab / Horizontal Tab (U+2B7E)
5. 🔒 Caps Lock (U+1F512)
6. 🔒 Caps Lock (U+1F512)
7. ↵ Return / Enter
8. ↵ Return / Enter
9. ⇪ Caps Lock
10. ⇧ Shift
11. ⇧ Shift
12. ⇧ Shift
13. ⇧ Shift
14. ⌘ Command (Apple/Mac)
15. ⌃ Control (Apple/Mac)
Icons Row 2:
1. <X| Backspace / Erase to the Left (U+232B)
2. <X| Backspace / Erase to the Left (U+232B)
3. <X| Backspace / Erase to the Left (U+232B)
4. ⎋ Escape (Apple Escape) [unicode U+238B]
5. O-->[ ] IBM print screen
6. Padlock with the Up and Down arrow: Scroll lock
7. ⎉Pause / Circled Horizontal Bar with Notch [U+2389]
8. a^ Insert IBM-style
9. a with curved line: Delete
10. ⌦Delete / Erase to the Right (U+2326)
11. ↖ Home / North West Arrow [U+2196]
12. ↘ End [unicode U+2198]
13. ⇞ Page up / Upwards Arrow with Double Stroke [U+21DE]
14. ⇟ Page down / downwards arrow with double stroke [U+21DF]
15. Padlock with the number “1” Num lock
16. ⎇Alt key with arrow (U+2387)
17. ◇Meta / UNIX-style super key / Diamond [U+25C7]
18. ⌃ Control 1.5U
19. ⌥ Option (alt) 1U [unicode U+2325]
20. ⌘ Command 1.5U
21. ⇮ Upwards Double Arrow (U+21EE)
22. List icon
23. ƒ Function / F with a hook [unicode U+0192]
24. ↵ Return / Enter