I'd love to help, here is a bit for you (I'm currently looking this up to help so this is NOT off the top of my head)
Kolechia

Kolechia is a neighbor country northwest of Arstotzka. After the 6-Year War, entrants from Kolechia are finally able to enter Arstotzka through the border town Grestin, although entrants from Kolechia are occasionally harassed by the Arstotzka government in an attempt to keep illegal immigrants and terrorists from crossing the borders.

Conditions in Kolechia are described as "ten times worse" than in Arstotzka by Sergiu.

Despite high hopes after the opening of the border, tension between Arstotzka and Kolechia keep growing throughout the game, up to the point where the future of the Grestin border checkpoint becomes uncertain. Depending on the choices the inspector makes during the story, Arstotzka and Kolechia may eventually find common ground and reach a tentative understanding, which will allow the border to remain open
Cities in Kolechia

Yurko City
Vedor
West Grestin

this was from the Papers, Please wiki on wikia

so essentially here are some ideas
UU- I don't know about that, maybe Terrorists?
UB- West Grestin Watchtower
UT- Kolechian terrorist strikes (they are the main impact in the timeframe of Papers, Please)- Kolechia gets an extra spy and spies have a 10% increase in effectiveness
ok, thanks ill be watching this discussion

Oh yeah and you could also just use the Kolechian stamp as the civ picture

Another thought is that you might want the Grestin Checkpoint its own civ

Obristan is a neighbor country north of Arstotzka.

Jorji Costava describes Obristan as beautiful in the winter. Obristan also comes off as more stable than war-torn Arstotzka. The inspector is given a choice to flee to Obristan, alone or with his family, when travel restrictions for Arstotzkan citizens are put in place on day 29. EZIC also evacuates the inspector's family to Obristan to safety in case he is arrested on day 23.

Obristan's signature phrase is "Obristan above all." This is similar to Arstotzka's "Glory to Arstotzka."

UU- I dunno, maybe Jorji as a joke (his documents say he is from Obristan)
UB- Obristanian refugee camp- works sort of like a hospital (you know, it increases population because, well, there are refugees moving in), but it decreases happiness
UT "Obristan Above All" or "peace in war" (this is a very war-torn region and Obristan is quite stable)- Obristan gets a 5 or 10% production boost if not at war

Cheers for the idea's man, I was thinking about using the icons from the passports already which you can half see I went to implementing in Arstotzka with the nation colours and I believe there's an old civ icon using the Arstotzkan passport image if you check the art...

Art is going to be the main issue here, UUs and UBs may have to use placeholder art or something similar.

Here are a few more ideas

The Pink Vice Brothel (you come down, i give you good girl)-culture
The "Get Big Town" gym- culture/production
The Truth of Arstotzka newspaper- increase happiness
Ministry of Labour-Could improve production
Ministry of Information-Provides an extra spy
Ministry of Trade-Increased gold from trade routes
Ministry of Admission-Reduces spy stealing rate
Ministry of Income-Gold
If you need more city names, then dont forget Nirsk-the Inspector's hometown.

Well, Republia actually has stuff you can use aside from the basic city names from Papers Please. Dukope, the creator of Papers Please, previously made another game in the same universe, called The Repulia Times. Link: http://dukope.com/
If you do decide to add in the other countries as civs, I'm sure you could use the Times as a UB or UA in some way.

Part of Orbistans passive civ bonus could be improved yields from snow and tundra tiles. It'd be a cute little nod to the "Snowier Pastures" bit from the game (as well as the achievement and the aforementioned improved stability in comparison to other countries).

I like the ideas so far, I think I'll start taking a look at what I can get into the mods for now and worry about artwork at a later date.

Originally posted by Mario Party of One:

Part of Orbistans passive civ bonus could be improved yields from snow and tundra tiles. It'd be a cute little nod to the "Snowier Pastures" bit from the game (as well as the achievement and the aforementioned improved stability in comparison to other countries).

I like that one

Britannia suggested the following "If you plan on doing Republia, the unique building could be the Ministory of Media from, increasing happiness and City State influence or something along those lines.
Perhaps their unique unit could be "Peace Squads" or the "Tactical Fighter".
Credit to "The Republia Times" for the suggestions!"

Seems like I should take a look at the republia times based on the amount of information it could add.

If you could get nilesey from the yogscast to voice one of the nations leader!

Approve of Orbistan. Arztotzka is best country.

Originally posted by Torel1:

If you could get nilesey from the yogscast to voice one of the nations leader!

Yes of course its an genius plan!

Originally posted by Jorji Costava:

Approve of Orbistan. Arztotzka is best country.

Jorji for the win!!!!