Since nobody else took up the challenge
1) Who was the first person to receive an "expert infantry" award from FISD? The first "expert infantry" John TK2036 (although EIB was not in the thread title ) , the first "Elite" Joey TK2126, the first "Mark IV" Scott TK4149
2) On the (now broken) EI listing page, what is the significance of the background images? Each costume version had background from the movie it was from, command staff had millennium falcon in death star landing bay
3) Who was the only person to be approved with an FX helmet? I thought a few did, Scott TK4149, also poll to remove FX helmet from EI program here
4) Who was the first ESB EIB? Mark TK8993
5) Who was the first Centurion? Mathias TK2959
6) Why can't you have more than one Centurion award?, Couldn't find the direct answer, did come across one of your posts "There are some valid reasons why the Centurion is a single reward, and part of that logic is so that people don't get so wrapped up at the top that we lose our focus on getting the other 1800 TK's brought up to par." post is here
7) Why were the colors chosen for the Centurion award? Based on the Roman Centurion theme, you mention it here
8) What was the first piece of EI merch ever created? 2008 EI coin thread here coin image here
9) Why are EI coins numbered and why can people only buy one? A singular incentive to reach EI level, numbered for tracking purposes
10) What FISD costumes has no one ever gotten to EI (or Centurion) Stormtrooper Concept Armor