It seems to me that this is not that difficult of a subject to consider. There are plenty of stories abounding about that time period, and should give you plenty of insights on what to do.
Are you planning on having a Sword and Sorcery (minus the sorcery) type campaign, using Traveller rules? Are you instead starting the characters off in such a locale and then have them be uplifted (something like the Idol Dreams scenario in the TNE mainbook)? Or are you just talking about your players visiting/crashing on such a world?
In any case, it should be obvious that things like swords and daggers and shields are going to be the stuff of the day. You'll have to walk everywhere, unless you have a riding animal. Settlements can't be all that big, and can't have hardly any structures higher than 2-4 stories (not counting palaces and deity monuments).
I hate to say this, but D&D and Warhammer (not 40k) will probably give you some good ideas, if you can wade through all the crap about magic and elves and such.
And don't rush to add psionics to your campaign. Psionics is something that should be rare and interesting, not as common as TV. It loses its specialness and ability to fascinate if it's too prevalent. I wouldn't let a player have it the first game, and MAYBE have an NPC with it.