The logo you listed as the 13th was actually picked for JDC 12, and was done by me. The Smooth Jazz one wasn't used sadly. The logo for JDC 13 was done by Sperry but I have zero memory of how it looked.

The same goes for the survivor end room logo - I made it for JDC 23, but I don't remember the JDC 22 logo at all.

Here's a list of the authors:

Ugly first two - no idea
8 - Spaztic
9 - Spaztic(?)
10 - Nightmare
11 - Eagle
faux 12 - Spaztic
12 - me
13 - Sperry
14 - P4ul
15 - Dalspots
16 - n00b
17 - Sperry
18 - Robee
19 - R3ptile/BlurredD
20 - Robee
21 - Robee
22 - don't remember, nor do I remember how it looked
23 - me
24 - Primpy
25 - me
26 - ?
27 - DarkClefita
28 - DarkClefita
29 - Who will be the Star of the next Logo Contest?