I made my avatar into Nana. Though I don't have that much gold, so this was the best I could do.
Ok, here's my guess at the avatars above:
1. Nobu
2. Shin
3. Hachi
4. Yasu
5. Nana
6.Ren
7.Misato
8. Reira
9. Takumi
10. Naoki
11. ?
12. Junko
13. Kyoske
14. ?
15. Reira's assistant?
16. Sachiko
17. Shouji
18. ?
Official NANA Guild 1st on Gaia