I have an Arc the Lad poster and a Lunar: TSSSC poster that I got from Kelly, but I haven't seen posters for their Turbo stuff before, and even only the Sega CD most of them (excepting Vay) only had pins for sale.
It was a lot harder for me to track their promo merchandise after they stopped putting fliers into their games near the end of the Saturn era. I mainly had to reply on whatever I heard from my local Babbages clerks.
I've used the web archive recently to find out most information that I can at this point since the site is gone, but
here's a link to a snapshot from mid-2004. If you click on the Merchandise link on the left you can see that they had a lot of promo stuff available including posters for most of the games you mentioned. Also feel free to cry at the prices when you see what they were originally sold for